| Age | Commit message (Collapse) | Author | Files | Lines |
|---|
|
Changes made by commit 796c2c23e14e ("zswap: replace RB tree with xarray")
are not reflected on a comment. Update the comment.
Link: https://lkml.kernel.org/r/20251003203851.43128-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
As the subject says.
Link: https://lkml.kernel.org/r/20251003203851.43128-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm/zswap: misc cleanup of code and documentations".
Clean up an unnecessary local variable write in incompressible pages
handling, typos (s/zwap/zswap/) and outdated comments/documentations about
the zswap's red-black tree, which is replaced by xarray.
This patch (of 4):
Incompressible pages handling logic in zswap_compress() is setting 'dlen'
as PAGE_SIZE twice. Once before deciding whether to save the content as
is, and once again after it is decided to save it as is. But the value of
'dlen' is used only if it is decided to save the content as is, so the
first write is unnecessary. It is not causing real user issues, but
making code confusing to read. Remove the unnecessary write operation.
Link: https://lkml.kernel.org/r/20251003203851.43128-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20251003203851.43128-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Chris Li <chrisl@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Swap cluster setup will try to shuffle the clusters on initialization. It
was helpful to avoid contention for the swap cache space. The cluster
size (2M) was much smaller than each swap cache space (64M), so shuffling
the cluster means the allocator will try to allocate swap slots that are
in different swap cache spaces for each CPU, reducing the chance of two
CPUs using the same swap cache space, and hence reducing the contention.
Now, swap cache is managed by swap clusters, this shuffle is pointless.
Just remove it, and clean up related macros.
This also improves the HDD swap performance as shuffling IO is a bad idea
for HDD, and now the shuffling is gone. Test have shown a ~40%
performance gain for HDD [1]:
Doing sequential swap in of 8G data using 8 processes with usemem, average
of 3 test runs:
Before: 1270.91 KB/s per process
After: 1849.54 KB/s per process
Link: https://lore.kernel.org/linux-mm/CAMgjq7AdauQ8=X0zeih2r21QoV=-WWj1hyBxLWRzq74n-C=-Ng@mail.gmail.com/ [1]
Link: https://lkml.kernel.org/r/20250916160100.31545-14-ryncsn@gmail.com
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202504241621.f27743ec-lkp@intel.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In preparation for replacing the swap cache backend with the swap table,
clean up and add proper kernel doc for all swap cache APIs. Now all swap
cache APIs are well-defined with consistent names.
No feature change, only renaming and documenting.
Link: https://lkml.kernel.org/r/20250916160100.31545-9-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm: remove zpool".
zpool is an indirection layer for zswap to switch between multiple
allocator backends at runtime. Since 6.15, zsmalloc is the only allocator
left in-tree, so there is no point in keeping zpool around.
This patch (of 3):
zswap goes through the zpool layer to enable runtime-switching of
allocator backends for compressed data. However, since zbud and z3fold
were removed in 6.15, zsmalloc has been the only option available.
As such, the zpool indirection is unnecessary. Make zswap deal with
zsmalloc directly. This is comparable to zram, which also directly
interacts with zsmalloc and has never supported a different backend.
Note that this does not preclude future improvements and experiments with
different allocation strategies. Should it become necessary, it's
possible to provide an alternate implementation for the zsmalloc API,
selectable at compile time. However, zsmalloc is also rather mature and
feature rich, with years of widespread production exposure; it's
encouraged to make incremental improvements rather than fork it.
In any case, the complexity of runtime pluggability seems excessive and
unjustified at this time. Switch zswap to zsmalloc to remove the last
user of the zpool API.
[hannes@cmpxchg.org: fix default compressr test]
Link: https://lkml.kernel.org/r/20250915153640.GA828739@cmpxchg.org
Link: https://lkml.kernel.org/r/20250829162212.208258-1-hannes@cmpxchg.org
Link: https://lkml.kernel.org/r/20250829162212.208258-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Nacked-by: Vitaly Wool <vitaly.wool@konsulko.se>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Reduce the compression buffer size from 2 * PAGE_SIZE to only one page, as
the compression output (in the success case) should not exceed the length
of the input.
In the past, Chengming tried to reduce the compression buffer size, but
ran into issues with the LZO algorithm (see [2]). Herbert Xu reported
that the issue has been fixed (see [3]). Now we should have the guarantee
that compressors' output should not exceed one page in the success case,
and the algorithm will just report failure otherwise.
With this patch, we save one page per cpu (per compression algorithm).
Link: https://lkml.kernel.org/r/20250820181547.3794167-1-nphamcs@gmail.com
Link: https://lore.kernel.org/linux-mm/20231213-zswap-dstmem-v4-1-f228b059dd89@bytedance.com/ [1]
Link: https://lore.kernel.org/lkml/0000000000000b05cd060d6b5511@google.com/ [2]
Link: https://lore.kernel.org/linux-mm/aKUmyl5gUFCdXGn-@gondor.apana.org.au/ [3]
Co-developed-by: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
When zswap writeback is enabled and it fails compressing a given page, the
page is swapped out to the backing swap device. This behavior breaks the
zswap's writeback LRU order, and hence users can experience unexpected
latency spikes. If the page is compressed without failure, but results in
a size of PAGE_SIZE, the LRU order is kept, but the decompression overhead
for loading the page back on the later access is unnecessary.
Keep the LRU order and optimize unnecessary decompression overheads in
those cases, by storing the original content as-is in zpool. The length
field of zswap_entry will be set appropriately, as PAGE_SIZE. Hence
whether it is saved as-is or not (whether decompression is unnecessary) is
identified by 'zswap_entry->length == PAGE_SIZE'.
Because the uncompressed data is saved in zpool, same to the compressed
ones, this introduces no change in terms of memory management including
movability and migratability of involved pages.
This change is also not increasing per zswap entry metadata overhead. But
as the number of incompressible pages increases, total zswap metadata
overhead is proportionally increased. The overhead should not be
problematic in usual cases, since the zswap metadata for single zswap
entry is much smaller than PAGE_SIZE, and in common zswap use cases there
should be a sufficient amount of compressible pages. Also it can be
mitigated by the zswap writeback.
When the writeback is disabled, the additional overhead could be
problematic. For the case, keep the current behavior that just returns
the failure and let swap_writeout() put the page back to the active LRU
list in the case.
Knowing how many incompressible pages are stored at the given moment will
be useful for future investigations. Add a new debugfs file called
stored_incompressible_pages for the purpose.
Tests
-----
I tested this patch using a simple self-written microbenchmark that is
available at GitHub[1]. You can reproduce the test I did by executing
run_tests.sh of the repo on your system. Note that the repo's
documentation is not good as of this writing, so you may need to read and
use the code.
The basic test scenario is simple. Run a test program making artificial
accesses to memory having artificial content under memory.high-set memory
limit and measure how many accesses were made in a given time.
The test program repeatedly and randomly access three anonymous memory
regions. The regions are all 500 MiB size, and be accessed in the same
probability. Two of those are filled up with a simple content that can
easily be compressed, while the remaining one is filled up with a content
that s read from /dev/urandom, which is easy to fail at compressing to a
size smaller than PAGE_SIZE. The program runs for two minutes and prints
out the number of accesses made every five seconds.
The test script runs the program under below four configurations.
- 0: memory.high is set to 2 GiB, zswap is disabled.
- 1-1: memory.high is set to 1350 MiB, zswap is disabled.
- 1-2: On 1-1, zswap is enabled without this patch.
- 1-3: On 1-2, this patch is applied.
For all zswap enabled cases, zswap shrinker is enabled.
Configuration '0' is for showing the original memory performance.
Configurations 1-1, 1-2 and 1-3 are for showing the performance of swap,
zswap, and this patch under a level of memory pressure (~10% of working
set). Configurations 0 and 1-1 are not the main focus of this patch, but
I'm adding those since their results transparently show how far this
microbenchmark test is from the real world.
Because the per-5 seconds performance is not very reliable, I measured the
average of that for the last one minute period of the test program run. I
also measured a few vmstat counters including zswpin, zswpout, zswpwb,
pswpin and pswpout during the test runs.
The measurement results are as below. To save space, I show performance
numbers that are normalized to that of the configuration '0' (no memory
pressure). The averaged accesses per 5 seconds of configuration '0' was
36493417.75.
config 0 1-1 1-2 1-3
perf_normalized 1.0000 0.0057 0.0235 0.0367
perf_stdev_ratio 0.0582 0.0652 0.0167 0.0346
zswpin 0 0 3548424 1999335
zswpout 0 0 3588817 2361689
zswpwb 0 0 10214 340270
pswpin 0 485806 772038 340967
pswpout 0 649543 144773 340270
'perf_normalized' is the performance metric, normalized to that of
configuration '0' (no pressure). 'perf_stdev_ratio' is the standard
deviation of the averaged data points, as a ratio to the averaged metric
value. For example, configuration '0' performance was showing 5.8% stdev.
Configurations 1-1 and 1-3 were having about 6.5% and 6.1% stdev. Also
the results were highly variable between multiple runs. So this result is
not very stable but just showing ball park figures. Please keep this in
your mind when reading these results.
Under about 10% of working set memory pressure, the performance was
dropped to about 0.57% of no-pressure one, when the normal swap is used
(1-1). Note that ~10% working set pressure is already extreme, at least
on this test setup. No one would desire system setups that can degrade
performance to 0.57% of the best case.
By turning zswap on (1-2), the performance was improved about 4x,
resulting in about 2.35% of no-pressure one. Because of the
incompressible pages in the third memory region, a significant amount of
(non-zswap) swap I/O operations were made, though.
By applying this patch (1-3), about 56% performance improvement was made,
resulting in about 3.67% of no-pressure one. Reduced pswpin of 1-3
compared to 1-2 let us see where this improvement came from.
Tests without Zswap Shrinker
----------------------------
Zswap shrinker is not enabled by default, so I ran the above test after
disabling zswap shrinker. The results are as below.
config 0 1-1 1-2 1-3
perf_normalized 1.0000 0.0056 0.0185 0.0260
perf_stdev_ratio 0.0467 0.0348 0.1832 0.3387
zswpin 0 0 2506765 6049078
zswpout 0 0 2534357 6115426
zswpwb 0 0 0 0
pswpin 0 463694 472978 0
pswpout 0 686227 612149 0
The overall normalized performance of the different configs are very
similar to those of zswap shrinker enabled case. By adding the memory
pressure, the performance was dropped to 0.56% of the original one. By
enabling zswap without zswap shrinker, the performance was increased to
1.85% of the original one. By applying this patch on it, the performance
was further increased to 2.6% of the original one.
Even though zswap shrinker is disabled, 1-2 shows high numbers of pswpin
and pswpout because the incompressible pages are directly swapped out. In
the case of 1-3, it shows zero pswpin and pswpout since it saves
incompressible pages in the memory, and shows higher performance.
Note that the performance of 1-2 and 1-3 varies pretty much. Standard
deviation of the performance for 1-2 was about 18.32% of the performance,
while that for 1-3 was about 33.87%. Because zswap shrinker is disabled
and the memory pressure is induced by memory.high, the workload got
penalty_jiffies sleeps, and this resulted in the unstabilized performance.
Related Works
-------------
This is not an entirely new attempt. Nhat Pham and Takero Funaki tried
very similar approaches in October 2023[2] and April 2024[3],
respectively. The two approaches didn't get merged mainly due to the
metadata overhead concern. I described why I think that shouldn't be a
problem for this change, which is automatically disabled when writeback is
disabled, at the beginning of this changelog.
This patch is not particularly different from those, and actually built
upon those. I wrote this from scratch again, though. Hence adding
Suggested-by tags for them. Actually Nhat first suggested this to me
offlist.
Historically, writeback disabling was introduced partially as a way to
solve the LRU order issue. Yosry pointed out[4] this is still suboptimal
when the incompressible pages are cold, since the incompressible pages
will continuously be tried to be zswapped out, and burn CPU cycles for
compression attempts that will anyway fail. One imaginable solution for
the problem is reusing the swapped-out page and its struct page to store
in the zswap pool. But that's out of the scope of this patch.
[sj@kernel.org: mark zswap_stored_incompressible_pages as static]
Link: https://lkml.kernel.org/r/20250821161750.78192-1-sj@kernel.org
[sj@kernel.org: v5]
Link: https://lkml.kernel.org/r/20250822190817.49287-1-sj@kernel.org
[sj@kernel.org: cleanup incompressible pages handling code]
Link: https://lkml.kernel.org/r/20250828163913.57957-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20250819193404.46680-1-sj@kernel.org
Link: https://github.com/sjp38/eval_zswap/blob/master/run.sh [1]
Link: https://lore.kernel.org/20231017003519.1426574-3-nphamcs@gmail.com [2]
Link: https://lore.kernel.org/20240706022523.1104080-6-flintglass@gmail.com [3]
Link: https://lore.kernel.org/CAJD7tkZXS-UJVAFfvxJ0nNgTzWBiqepPYA4hEozi01_qktkitg@mail.gmail.com [4]
Signed-off-by: SeongJae Park <sj@kernel.org>
Suggested-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Takero Funaki <flintglass@gmail.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
__swap_writepage only needs the swap_iocb cookie from the
writeback_control structure, so pass it explicitly and remove the now
unused swap_iocb member from struct writeback_control.
Link: https://lkml.kernel.org/r/20250610054959.2057526-5-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently, zsmalloc, zswap's and zram's backend memory allocator, does not
enforce any policy for the allocation of memory for the compressed data,
instead just adopting the memory policy of the task entering reclaim, or
the default policy (prefer local node) if no such policy is specified.
This can lead to several pathological behaviors in multi-node NUMA
systems:
1. Systems with CXL-based memory tiering can encounter the following
inversion with zswap/zram: the coldest pages demoted to the CXL tier
can return to the high tier when they are reclaimed to compressed swap,
creating memory pressure on the high tier.
2. Consider a direct reclaimer scanning nodes in order of allocation
preference. If it ventures into remote nodes, the memory it compresses
there should stay there. Trying to shift those contents over to the
reclaiming thread's preferred node further *increases* its local
pressure, and provoking more spills. The remote node is also the most
likely to refault this data again. This undesirable behavior was
pointed out by Johannes Weiner in [1].
3. For zswap writeback, the zswap entries are organized in
node-specific LRUs, based on the node placement of the original pages,
allowing for targeted zswap writeback for specific nodes.
However, the compressed data of a zswap entry can be placed on a
different node from the LRU it is placed on. This means that reclaim
targeted at one node might not free up memory used for zswap entries in
that node, but instead reclaiming memory in a different node.
All of these issues will be resolved if the compressed data go to the same
node as the original page. This patch encourages this behavior by having
zswap and zram pass the node of the original page to zsmalloc, and have
zsmalloc prefer the specified node if we need to allocate new (zs)pages
for the compressed data.
Note that we are not strictly binding the allocation to the preferred
node. We still allow the allocation to fall back to other nodes when the
preferred node is full, or if we have zspages with slots available on a
different node. This is OK, and still a strict improvement over the
status quo:
1. On a system with demotion enabled, we will generally prefer
demotions over compressed swapping, and only swap when pages have
already gone to the lowest tier. This patch should achieve the desired
effect for the most part.
2. If the preferred node is out of memory, letting the compressed data
going to other nodes can be better than the alternative (OOMs, keeping
cold memory unreclaimed, disk swapping, etc.).
3. If the allocation go to a separate node because we have a zspage
with slots available, at least we're not creating extra immediate
memory pressure (since the space is already allocated).
3. While there can be mixings, we generally reclaim pages in same-node
batches, which encourage zspage grouping that is more likely to go to
the right node.
4. A strict binding would require partitioning zsmalloc by node, which
is more complicated, and more prone to regression, since it reduces the
storage density of zsmalloc. We need to evaluate the tradeoff and
benchmark carefully before adopting such an involved solution.
[1]: https://lore.kernel.org/linux-mm/20250331165306.GC2110528@cmpxchg.org/
[senozhatsky@chromium.org: coding-style fixes]
Link: https://lkml.kernel.org/r/mnvexa7kseswglcqbhlot4zg3b3la2ypv2rimdl5mh5glbmhvz@wi6bgqn47hge
Link: https://lkml.kernel.org/r/20250402204416.3435994-1-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Gregory Price <gourry@gourry.net>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org> [zram, zsmalloc]
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev> [zswap/zsmalloc]
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Joanthan Cameron <Jonathan.Cameron@huawei.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently, zswap_cpu_comp_dead() calls crypto_free_acomp() while holding
the per-CPU acomp_ctx mutex. crypto_free_acomp() then holds scomp_lock
(through crypto_exit_scomp_ops_async()).
On the other hand, crypto_alloc_acomp_node() holds the scomp_lock (through
crypto_scomp_init_tfm()), and then allocates memory. If the allocation
results in reclaim, we may attempt to hold the per-CPU acomp_ctx mutex.
The above dependencies can cause an ABBA deadlock. For example in the
following scenario:
(1) Task A running on CPU #1:
crypto_alloc_acomp_node()
Holds scomp_lock
Enters reclaim
Reads per_cpu_ptr(pool->acomp_ctx, 1)
(2) Task A is descheduled
(3) CPU #1 goes offline
zswap_cpu_comp_dead(CPU #1)
Holds per_cpu_ptr(pool->acomp_ctx, 1))
Calls crypto_free_acomp()
Waits for scomp_lock
(4) Task A running on CPU #2:
Waits for per_cpu_ptr(pool->acomp_ctx, 1) // Read on CPU #1
DEADLOCK
Since there is no requirement to call crypto_free_acomp() with the per-CPU
acomp_ctx mutex held in zswap_cpu_comp_dead(), move it after the mutex is
unlocked. Also move the acomp_request_free() and kfree() calls for
consistency and to avoid any potential sublte locking dependencies in the
future.
With this, only setting acomp_ctx fields to NULL occurs with the mutex
held. This is similar to how zswap_cpu_comp_prepare() only initializes
acomp_ctx fields with the mutex held, after performing all allocations
before holding the mutex.
Opportunistically, move the NULL check on acomp_ctx so that it takes place
before the mutex dereference.
Link: https://lkml.kernel.org/r/20250226185625.2672936-1-yosry.ahmed@linux.dev
Fixes: 12dcb0ef5406 ("mm: zswap: properly synchronize freeing resources during CPU hotunplug")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Co-developed-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Reported-by: syzbot+1a517ccfcbc6a7ab0f82@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67bcea51.050a0220.bbfd1.0096.GAE@google.com/
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Nhat Pham <nphamcs@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Chris Murphy <lists@colorremedies.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently, we crash the kernel when a decompression failure occurs in
zswap (either because of memory corruption, or a bug in the compression
algorithm). This is overkill. We should only SIGBUS the unfortunate
process asking for the zswap entry on zswap load, and skip the corrupted
entry in zswap writeback.
See [1] for a recent upstream discussion about this.
The zswap writeback case is relatively straightforward to fix. For the
zswap_load() case, we change the return behavior:
* Return 0 on success.
* Return -ENOENT (with the folio locked) if zswap does not own the
swapped out content.
* Return -EIO if zswap owns the swapped out content, but encounters a
decompression failure for some reasons. The folio will be unlocked,
but not be marked up-to-date, which will eventually cause the process
requesting the page to SIGBUS (see the handling of not-up-to-date
folio in do_swap_page() in mm/memory.c), without crashing the kernel.
* Return -EINVAL if we encounter a large folio, as large folio should
not be swapped in while zswap is being used. Similar to the -EIO case,
we also unlock the folio but do not mark it as up-to-date to SIGBUS
the faulting process.
As a side effect, we require one extra zswap tree traversal in the load
and writeback paths. Quick benchmarking on a kernel build test shows no
performance difference:
With the new scheme:
real: mean: 125.1s, stdev: 0.12s
user: mean: 3265.23s, stdev: 9.62s
sys: mean: 2156.41s, stdev: 13.98s
The old scheme:
real: mean: 125.78s, stdev: 0.45s
user: mean: 3287.18s, stdev: 5.95s
sys: mean: 2177.08s, stdev: 26.52s
[nphamcs@gmail.com: fix documentation of zswap_load()]
Link: https://lkml.kernel.org/r/20250306222453.1269456-1-nphamcs@gmail.com
Link: https://lore.kernel.org/all/ZsiLElTykamcYZ6J@casper.infradead.org/ [1]
Link: https://lkml.kernel.org/r/20250306205011.784787-1-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Suggested-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
zpool_malloc_support_movable() always returns true for zsmalloc, the only
remaining zpool driver. Remove it and set the gfp flags in
zswap_compress() accordingly. Opportunistically use GFP_NOWAIT instead of
__GFP_NOWARN | __GFP_KSWAPD_RECLAIM for conciseness as they are
equivalent.
Link: https://lkml.kernel.org/r/20250305061134.4105762-6-yosry.ahmed@linux.dev
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Use the new object read/write APIs instead of mapping APIs.
On compress side, zpool_obj_write() is more concise and provides exactly
what zswap needs to write the compressed object to the zpool, instead of
map->copy->unmap.
On the decompress side, zpool_obj_read_begin() is sleepable, which
allows avoiding the memcpy() for zsmalloc and slightly simplifying the
code by:
- Avoiding checking if the zpool driver is sleepable, reducing special
cases and shrinking the huge comment.
- Having a single zpool_obj_read_end() call rather than multiple
conditional zpool_unmap_handle() calls.
The !virt_addr_valid() case can be removed in the future if the crypto API
supports kmap addresses or by using kmap_to_page(), completely eliminating
the memcpy() path in zswap_decompress(). This a step toward that. In
that spirit, opportunistically make the comment more specific about the
kmap case instead of generic non-linear addresses. This is the only case
that needs to be handled in practice, and the generic comment makes it
seem like a bigger problem that it actually is.
Link: https://lkml.kernel.org/r/20250305061134.4105762-3-yosry.ahmed@linux.dev
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently __read_swap_cache_async() has get/put_swap_device() calls to
increase/decrease a swap device reference to prevent swapoff. While some
of its callers have already held the swap device reference, e.g in
do_swap_page() and shmem_swapin_folio() where __read_swap_cache_async()
will finally called. Now there are only two callers not holding a swap
device reference, so make them hold a reference instead. And drop the
get/put_swap_device calls in __read_swap_cache_async. This should reduce
the overhead for swap in during page fault slightly.
Link: https://lkml.kernel.org/r/20250313165935.63303-4-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
This is currently the only atomic_long_t variable initialized by
ATOMIC_INIT macro found in the kernel by using `grep -r atomic_long_t |
grep ATOMIC_INIT`
This was introduced in 6e1fa555ec77, in which we modified the type of
zswap_stored_pages to atomic_long_t, but didn't change the initialization.
Link: https://lkml.kernel.org/r/20250226153253.19179-1-sunk67188@gmail.com
Fixes: 6e1fa555ec77 ("mm: zswap: modify zswap_stored_pages to be atomic_long_t")
Signed-off-by: Sun YangKai <sunk67188@gmail.com>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Commit b7c0ccdfbafd ("mm: zswap: support large folios in zswap_store()")
skips charging any zswap entries when it failed to zswap the entire folio.
However, when some base pages are zswapped but it failed to zswap the
entire folio, the zswap operation is rolled back. When freeing zswap
entries for those pages, zswap_entry_free() uncharges the zswap entries
that were not previously charged, causing zswap charging to become
inconsistent.
This inconsistency triggers two warnings with following steps:
# On a machine with 64GiB of RAM and 36GiB of zswap
$ stress-ng --bigheap 2 # wait until the OOM-killer kills stress-ng
$ sudo reboot
The two warnings are:
in mm/memcontrol.c:163, function obj_cgroup_release():
WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1));
in mm/page_counter.c:60, function page_counter_cancel():
if (WARN_ONCE(new < 0, "page_counter underflow: %ld nr_pages=%lu\n",
new, nr_pages))
zswap_stored_pages also becomes inconsistent in the same way.
As suggested by Kanchana, increment zswap_stored_pages and charge zswap
entries within zswap_store_page() when it succeeds. This way,
zswap_entry_free() will decrement the counter and uncharge the entries
when it failed to zswap the entire folio.
While this could potentially be optimized by batching objcg charging and
incrementing the counter, let's focus on fixing the bug this time and
leave the optimization for later after some evaluation.
After resolving the inconsistency, the warnings disappear.
[42.hyeyoo@gmail.com: refactor zswap_store_page()]
Link: https://lkml.kernel.org/r/20250131082037.2426-1-42.hyeyoo@gmail.com
Link: https://lkml.kernel.org/r/20250129100844.2935-1-42.hyeyoo@gmail.com
Fixes: b7c0ccdfbafd ("mm: zswap: support large folios in zswap_store()")
Co-developed-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
"The various patchsets are summarized below. Plus of course many
indivudual patches which are described in their changelogs.
- "Allocate and free frozen pages" from Matthew Wilcox reorganizes
the page allocator so we end up with the ability to allocate and
free zero-refcount pages. So that callers (ie, slab) can avoid a
refcount inc & dec
- "Support large folios for tmpfs" from Baolin Wang teaches tmpfs to
use large folios other than PMD-sized ones
- "Fix mm/rodata_test" from Petr Tesarik performs some maintenance
and fixes for this small built-in kernel selftest
- "mas_anode_descend() related cleanup" from Wei Yang tidies up part
of the mapletree code
- "mm: fix format issues and param types" from Keren Sun implements a
few minor code cleanups
- "simplify split calculation" from Wei Yang provides a few fixes and
a test for the mapletree code
- "mm/vma: make more mmap logic userland testable" from Lorenzo
Stoakes continues the work of moving vma-related code into the
(relatively) new mm/vma.c
- "mm/page_alloc: gfp flags cleanups for alloc_contig_*()" from David
Hildenbrand cleans up and rationalizes handling of gfp flags in the
page allocator
- "readahead: Reintroduce fix for improper RA window sizing" from Jan
Kara is a second attempt at fixing a readahead window sizing issue.
It should reduce the amount of unnecessary reading
- "synchronously scan and reclaim empty user PTE pages" from Qi Zheng
addresses an issue where "huge" amounts of pte pagetables are
accumulated:
https://lore.kernel.org/lkml/cover.1718267194.git.zhengqi.arch@bytedance.com/
Qi's series addresses this windup by synchronously freeing PTE
memory within the context of madvise(MADV_DONTNEED)
- "selftest/mm: Remove warnings found by adding compiler flags" from
Muhammad Usama Anjum fixes some build warnings in the selftests
code when optional compiler warnings are enabled
- "mm: don't use __GFP_HARDWALL when migrating remote pages" from
David Hildenbrand tightens the allocator's observance of
__GFP_HARDWALL
- "pkeys kselftests improvements" from Kevin Brodsky implements
various fixes and cleanups in the MM selftests code, mainly
pertaining to the pkeys tests
- "mm/damon: add sample modules" from SeongJae Park enhances DAMON to
estimate application working set size
- "memcg/hugetlb: Rework memcg hugetlb charging" from Joshua Hahn
provides some cleanups to memcg's hugetlb charging logic
- "mm/swap_cgroup: remove global swap cgroup lock" from Kairui Song
removes the global swap cgroup lock. A speedup of 10% for a
tmpfs-based kernel build was demonstrated
- "zram: split page type read/write handling" from Sergey Senozhatsky
has several fixes and cleaups for zram in the area of
zram_write_page(). A watchdog softlockup warning was eliminated
- "move pagetable_*_dtor() to __tlb_remove_table()" from Kevin
Brodsky cleans up the pagetable destructor implementations. A rare
use-after-free race is fixed
- "mm/debug: introduce and use VM_WARN_ON_VMG()" from Lorenzo Stoakes
simplifies and cleans up the debugging code in the VMA merging
logic
- "Account page tables at all levels" from Kevin Brodsky cleans up
and regularizes the pagetable ctor/dtor handling. This results in
improvements in accounting accuracy
- "mm/damon: replace most damon_callback usages in sysfs with new
core functions" from SeongJae Park cleans up and generalizes
DAMON's sysfs file interface logic
- "mm/damon: enable page level properties based monitoring" from
SeongJae Park increases the amount of information which is
presented in response to DAMOS actions
- "mm/damon: remove DAMON debugfs interface" from SeongJae Park
removes DAMON's long-deprecated debugfs interfaces. Thus the
migration to sysfs is completed
- "mm/hugetlb: Refactor hugetlb allocation resv accounting" from
Peter Xu cleans up and generalizes the hugetlb reservation
accounting
- "mm: alloc_pages_bulk: small API refactor" from Luiz Capitulino
removes a never-used feature of the alloc_pages_bulk() interface
- "mm/damon: extend DAMOS filters for inclusion" from SeongJae Park
extends DAMOS filters to support not only exclusion (rejecting),
but also inclusion (allowing) behavior
- "Add zpdesc memory descriptor for zswap.zpool" from Alex Shi
introduces a new memory descriptor for zswap.zpool that currently
overlaps with struct page for now. This is part of the effort to
reduce the size of struct page and to enable dynamic allocation of
memory descriptors
- "mm, swap: rework of swap allocator locks" from Kairui Song redoes
and simplifies the swap allocator locking. A speedup of 400% was
demonstrated for one workload. As was a 35% reduction for kernel
build time with swap-on-zram
- "mm: update mips to use do_mmap(), make mmap_region() internal"
from Lorenzo Stoakes reworks MIPS's use of mmap_region() so that
mmap_region() can be made MM-internal
- "mm/mglru: performance optimizations" from Yu Zhao fixes a few
MGLRU regressions and otherwise improves MGLRU performance
- "Docs/mm/damon: add tuning guide and misc updates" from SeongJae
Park updates DAMON documentation
- "Cleanup for memfd_create()" from Isaac Manjarres does that thing
- "mm: hugetlb+THP folio and migration cleanups" from David
Hildenbrand provides various cleanups in the areas of hugetlb
folios, THP folios and migration
- "Uncached buffered IO" from Jens Axboe implements the new
RWF_DONTCACHE flag which provides synchronous dropbehind for
pagecache reading and writing. To permite userspace to address
issues with massive buildup of useless pagecache when
reading/writing fast devices
- "selftests/mm: virtual_address_range: Reduce memory" from Thomas
Weißschuh fixes and optimizes some of the MM selftests"
* tag 'mm-stable-2025-01-26-14-59' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits)
mm/compaction: fix UBSAN shift-out-of-bounds warning
s390/mm: add missing ctor/dtor on page table upgrade
kasan: sw_tags: use str_on_off() helper in kasan_init_sw_tags()
tools: add VM_WARN_ON_VMG definition
mm/damon/core: use str_high_low() helper in damos_wmark_wait_us()
seqlock: add missing parameter documentation for raw_seqcount_try_begin()
mm/page-writeback: consolidate wb_thresh bumping logic into __wb_calc_thresh
mm/page_alloc: remove the incorrect and misleading comment
zram: remove zcomp_stream_put() from write_incompressible_page()
mm: separate move/undo parts from migrate_pages_batch()
mm/kfence: use str_write_read() helper in get_access_type()
selftests/mm/mkdirty: fix memory leak in test_uffdio_copy()
kasan: hw_tags: Use str_on_off() helper in kasan_init_hw_tags()
selftests/mm: virtual_address_range: avoid reading from VM_IO mappings
selftests/mm: vm_util: split up /proc/self/smaps parsing
selftests/mm: virtual_address_range: unmap chunks after validation
selftests/mm: virtual_address_range: mmap() without PROT_WRITE
selftests/memfd/memfd_test: fix possible NULL pointer dereference
mm: add FGP_DONTCACHE folio creation flag
mm: call filemap_fdatawrite_range_kick() after IOCB_DONTCACHE issue
...
|
|
In zswap_cpu_comp_prepare(), allocations are made and assigned to various
members of acomp_ctx under acomp_ctx->mutex. However, allocations may
recurse into zswap through reclaim, trying to acquire the same mutex and
deadlocking.
Move the allocations before the mutex critical section. Only the
initialization of acomp_ctx needs to be done with the mutex held.
Link: https://lkml.kernel.org/r/20250113214458.2123410-1-yosryahmed@google.com
Fixes: 12dcb0ef5406 ("mm: zswap: properly synchronize freeing resources during CPU hotunplug")
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
This function has been able to return LRU_STOP since commit b49547ade38a
("mm/zswap: stop lru list shrinking when encounter warm region"). To
reduce confusion, update the comment to also list LRU_STOP as an option.
Link: https://lkml.kernel.org/r/20241127-lru-stop-comment-v1-1-f54a7cba9429@google.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In zswap_compress() and zswap_decompress(), the per-CPU acomp_ctx of the
current CPU at the beginning of the operation is retrieved and used
throughout. However, since neither preemption nor migration are disabled,
it is possible that the operation continues on a different CPU.
If the original CPU is hotunplugged while the acomp_ctx is still in use,
we run into a UAF bug as some of the resources attached to the acomp_ctx
are freed during hotunplug in zswap_cpu_comp_dead() (i.e.
acomp_ctx.buffer, acomp_ctx.req, or acomp_ctx.acomp).
The problem was introduced in commit 1ec3b5fe6eec ("mm/zswap: move to use
crypto_acomp API for hardware acceleration") when the switch to the
crypto_acomp API was made. Prior to that, the per-CPU crypto_comp was
retrieved using get_cpu_ptr() which disables preemption and makes sure the
CPU cannot go away from under us. Preemption cannot be disabled with the
crypto_acomp API as a sleepable context is needed.
Use the acomp_ctx.mutex to synchronize CPU hotplug callbacks allocating
and freeing resources with compression/decompression paths. Make sure
that acomp_ctx.req is NULL when the resources are freed. In the
compression/decompression paths, check if acomp_ctx.req is NULL after
acquiring the mutex (meaning the CPU was offlined) and retry on the new
CPU.
The initialization of acomp_ctx.mutex is moved from the CPU hotplug
callback to the pool initialization where it belongs (where the mutex is
allocated). In addition to adding clarity, this makes sure that CPU
hotplug cannot reinitialize a mutex that is already locked by
compression/decompression.
Previously a fix was attempted by holding cpus_read_lock() [1]. This
would have caused a potential deadlock as it is possible for code already
holding the lock to fall into reclaim and enter zswap (causing a
deadlock). A fix was also attempted using SRCU for synchronization, but
Johannes pointed out that synchronize_srcu() cannot be used in CPU hotplug
notifiers [2].
Alternative fixes that were considered/attempted and could have worked:
- Refcounting the per-CPU acomp_ctx. This involves complexity in
handling the race between the refcount dropping to zero in
zswap_[de]compress() and the refcount being re-initialized when the
CPU is onlined.
- Disabling migration before getting the per-CPU acomp_ctx [3], but
that's discouraged and is a much bigger hammer than needed, and could
result in subtle performance issues.
[1]https://lkml.kernel.org/20241219212437.2714151-1-yosryahmed@google.com/
[2]https://lkml.kernel.org/20250107074724.1756696-2-yosryahmed@google.com/
[3]https://lkml.kernel.org/20250107222236.2715883-2-yosryahmed@google.com/
[yosryahmed@google.com: remove comment]
Link: https://lkml.kernel.org/r/CAJD7tkaxS1wjn+swugt8QCvQ-rVF5RZnjxwPGX17k8x9zSManA@mail.gmail.com
Link: https://lkml.kernel.org/r/20250108222441.3622031-1-yosryahmed@google.com
Fixes: 1ec3b5fe6eec ("mm/zswap: move to use crypto_acomp API for hardware acceleration")
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reported-by: Johannes Weiner <hannes@cmpxchg.org>
Closes: https://lore.kernel.org/lkml/20241113213007.GB1564047@cmpxchg.org/
Reported-by: Sam Sun <samsun1006219@gmail.com>
Closes: https://lore.kernel.org/lkml/CAEkJfYMtSdM5HceNsXUDf5haghD5+o2e7Qv4OcuruL4tPg6OaQ@mail.gmail.com/
Cc: Barry Song <baohua@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
This reverts commit eaebeb93922ca6ab0dd92027b73d0112701706ef.
Commit eaebeb93922c ("mm: zswap: fix race between [de]compression and CPU
hotunplug") used the CPU hotplug lock in zswap compress/decompress
operations to protect against a race with CPU hotunplug making some
per-CPU resources go away.
However, zswap compress/decompress can be reached through reclaim while
the lock is held, resulting in a potential deadlock as reported by syzbot:
======================================================
WARNING: possible circular locking dependency detected
6.13.0-rc6-syzkaller-00006-g5428dc1906dd #0 Not tainted
------------------------------------------------------
kswapd0/89 is trying to acquire lock:
ffffffff8e7d2ed0 (cpu_hotplug_lock){++++}-{0:0}, at: acomp_ctx_get_cpu mm/zswap.c:886 [inline]
ffffffff8e7d2ed0 (cpu_hotplug_lock){++++}-{0:0}, at: zswap_compress mm/zswap.c:908 [inline]
ffffffff8e7d2ed0 (cpu_hotplug_lock){++++}-{0:0}, at: zswap_store_page mm/zswap.c:1439 [inline]
ffffffff8e7d2ed0 (cpu_hotplug_lock){++++}-{0:0}, at: zswap_store+0xa74/0x1ba0 mm/zswap.c:1546
but task is already holding lock:
ffffffff8ea355a0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6871 [inline]
ffffffff8ea355a0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb58/0x2f30 mm/vmscan.c:7253
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (fs_reclaim){+.+.}-{0:0}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
__fs_reclaim_acquire mm/page_alloc.c:3853 [inline]
fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3867
might_alloc include/linux/sched/mm.h:318 [inline]
slab_pre_alloc_hook mm/slub.c:4070 [inline]
slab_alloc_node mm/slub.c:4148 [inline]
__kmalloc_cache_node_noprof+0x40/0x3a0 mm/slub.c:4337
kmalloc_node_noprof include/linux/slab.h:924 [inline]
alloc_worker kernel/workqueue.c:2638 [inline]
create_worker+0x11b/0x720 kernel/workqueue.c:2781
workqueue_prepare_cpu+0xe3/0x170 kernel/workqueue.c:6628
cpuhp_invoke_callback+0x48d/0x830 kernel/cpu.c:194
__cpuhp_invoke_callback_range kernel/cpu.c:965 [inline]
cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
cpuhp_up_callbacks kernel/cpu.c:1020 [inline]
_cpu_up+0x2b3/0x580 kernel/cpu.c:1690
cpu_up+0x184/0x230 kernel/cpu.c:1722
cpuhp_bringup_mask+0xdf/0x260 kernel/cpu.c:1788
cpuhp_bringup_cpus_parallel+0xf9/0x160 kernel/cpu.c:1878
bringup_nonboot_cpus+0x2b/0x50 kernel/cpu.c:1892
smp_init+0x34/0x150 kernel/smp.c:1009
kernel_init_freeable+0x417/0x5d0 init/main.c:1569
kernel_init+0x1d/0x2b0 init/main.c:1466
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
-> #0 (cpu_hotplug_lock){++++}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
__lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
cpus_read_lock+0x42/0x150 kernel/cpu.c:490
acomp_ctx_get_cpu mm/zswap.c:886 [inline]
zswap_compress mm/zswap.c:908 [inline]
zswap_store_page mm/zswap.c:1439 [inline]
zswap_store+0xa74/0x1ba0 mm/zswap.c:1546
swap_writepage+0x647/0xce0 mm/page_io.c:279
shmem_writepage+0x1248/0x1610 mm/shmem.c:1579
pageout mm/vmscan.c:696 [inline]
shrink_folio_list+0x35ee/0x57e0 mm/vmscan.c:1374
shrink_inactive_list mm/vmscan.c:1967 [inline]
shrink_list mm/vmscan.c:2205 [inline]
shrink_lruvec+0x16db/0x2f30 mm/vmscan.c:5734
mem_cgroup_shrink_node+0x385/0x8e0 mm/vmscan.c:6575
mem_cgroup_soft_reclaim mm/memcontrol-v1.c:312 [inline]
memcg1_soft_limit_reclaim+0x346/0x810 mm/memcontrol-v1.c:362
balance_pgdat mm/vmscan.c:6975 [inline]
kswapd+0x17b3/0x2f30 mm/vmscan.c:7253
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(fs_reclaim);
lock(cpu_hotplug_lock);
lock(fs_reclaim);
rlock(cpu_hotplug_lock);
*** DEADLOCK ***
1 lock held by kswapd0/89:
#0: ffffffff8ea355a0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6871 [inline]
#0: ffffffff8ea355a0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb58/0x2f30 mm/vmscan.c:7253
stack backtrace:
CPU: 0 UID: 0 PID: 89 Comm: kswapd0 Not tainted 6.13.0-rc6-syzkaller-00006-g5428dc1906dd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
__lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
cpus_read_lock+0x42/0x150 kernel/cpu.c:490
acomp_ctx_get_cpu mm/zswap.c:886 [inline]
zswap_compress mm/zswap.c:908 [inline]
zswap_store_page mm/zswap.c:1439 [inline]
zswap_store+0xa74/0x1ba0 mm/zswap.c:1546
swap_writepage+0x647/0xce0 mm/page_io.c:279
shmem_writepage+0x1248/0x1610 mm/shmem.c:1579
pageout mm/vmscan.c:696 [inline]
shrink_folio_list+0x35ee/0x57e0 mm/vmscan.c:1374
shrink_inactive_list mm/vmscan.c:1967 [inline]
shrink_list mm/vmscan.c:2205 [inline]
shrink_lruvec+0x16db/0x2f30 mm/vmscan.c:5734
mem_cgroup_shrink_node+0x385/0x8e0 mm/vmscan.c:6575
mem_cgroup_soft_reclaim mm/memcontrol-v1.c:312 [inline]
memcg1_soft_limit_reclaim+0x346/0x810 mm/memcontrol-v1.c:362
balance_pgdat mm/vmscan.c:6975 [inline]
kswapd+0x17b3/0x2f30 mm/vmscan.c:7253
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Revert the change. A different fix for the race with CPU hotunplug will
follow.
Link: https://lkml.kernel.org/r/20250107222236.2715883-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sam Sun <samsun1006219@gmail.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In zswap_compress() and zswap_decompress(), the per-CPU acomp_ctx of the
current CPU at the beginning of the operation is retrieved and used
throughout. However, since neither preemption nor migration are disabled,
it is possible that the operation continues on a different CPU.
If the original CPU is hotunplugged while the acomp_ctx is still in use,
we run into a UAF bug as the resources attached to the acomp_ctx are freed
during hotunplug in zswap_cpu_comp_dead().
The problem was introduced in commit 1ec3b5fe6eec ("mm/zswap: move to use
crypto_acomp API for hardware acceleration") when the switch to the
crypto_acomp API was made. Prior to that, the per-CPU crypto_comp was
retrieved using get_cpu_ptr() which disables preemption and makes sure the
CPU cannot go away from under us. Preemption cannot be disabled with the
crypto_acomp API as a sleepable context is needed.
Commit 8ba2f844f050 ("mm/zswap: change per-cpu mutex and buffer to
per-acomp_ctx") increased the UAF surface area by making the per-CPU
buffers dynamic, adding yet another resource that can be freed from under
zswap compression/decompression by CPU hotunplug.
There are a few ways to fix this:
(a) Add a refcount for acomp_ctx.
(b) Disable migration while using the per-CPU acomp_ctx.
(c) Disable CPU hotunplug while using the per-CPU acomp_ctx by holding
the CPUs read lock.
Implement (c) since it's simpler than (a), and (b) involves using
migrate_disable() which is apparently undesired (see huge comment in
include/linux/preempt.h).
Link: https://lkml.kernel.org/r/20241219212437.2714151-1-yosryahmed@google.com
Fixes: 1ec3b5fe6eec ("mm/zswap: move to use crypto_acomp API for hardware acceleration")
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reported-by: Johannes Weiner <hannes@cmpxchg.org>
Closes: https://lore.kernel.org/lkml/20241113213007.GB1564047@cmpxchg.org/
Reported-by: Sam Sun <samsun1006219@gmail.com>
Closes: https://lore.kernel.org/lkml/CAEkJfYMtSdM5HceNsXUDf5haghD5+o2e7Qv4OcuruL4tPg6OaQ@mail.gmail.com/
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Barry Song <baohua@kernel.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Now isolation no longer takes the list_lru global node lock, only use the
per-cgroup lock instead. And this lock is inside the list_lru_one being
walked, no longer needed to pass the lock explicitly.
Link: https://lkml.kernel.org/r/20241104175257.60853-7-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently, every list_lru has a per-node lock that protects adding,
deletion, isolation, and reparenting of all list_lru_one instances
belonging to this list_lru on this node. This lock contention is heavy
when multiple cgroups modify the same list_lru.
This lock can be split into per-cgroup scope to reduce contention.
To achieve this, we need a stable list_lru_one for every cgroup. This
commit adds a lock to each list_lru_one and introduced a helper function
lock_list_lru_of_memcg, making it possible to pin the list_lru of a memcg.
Then reworked the reparenting process.
Reparenting will switch the list_lru_one instances one by one. By locking
each instance and marking it dead using the nr_items counter, reparenting
ensures that all items in the corresponding cgroup (on-list or not,
because items have a stable cgroup, see below) will see the list_lru_one
switch synchronously.
Objcg reparent is also moved after list_lru reparent so items will have a
stable mem cgroup until all list_lru_one instances are drained.
The only caller that doesn't work the *_obj interfaces are direct calls to
list_lru_{add,del}. But it's only used by zswap and that's also based on
objcg, so it's fine.
This also changes the bahaviour of the isolation function when LRU_RETRY
or LRU_REMOVED_RETRY is returned, because now releasing the lock could
unblock reparenting and free the list_lru_one, isolation function will
have to return withoug re-lock the lru.
prepare() {
mkdir /tmp/test-fs
modprobe brd rd_nr=1 rd_size=33554432
mkfs.xfs -f /dev/ram0
mount -t xfs /dev/ram0 /tmp/test-fs
for i in $(seq 1 512); do
mkdir "/tmp/test-fs/$i"
for j in $(seq 1 10240); do
echo TEST-CONTENT > "/tmp/test-fs/$i/$j"
done &
done; wait
}
do_test() {
read_worker() {
sleep 1
tar -cv "$1" &>/dev/null
}
read_in_all() {
cd "/tmp/test-fs" && ls
for i in $(seq 1 512); do
(exec sh -c 'echo "$PPID"') > "/sys/fs/cgroup/benchmark/$i/cgroup.procs"
read_worker "$i" &
done; wait
}
for i in $(seq 1 512); do
mkdir -p "/sys/fs/cgroup/benchmark/$i"
done
echo +memory > /sys/fs/cgroup/benchmark/cgroup.subtree_control
echo 512M > /sys/fs/cgroup/benchmark/memory.max
echo 3 > /proc/sys/vm/drop_caches
time read_in_all
}
Above script simulates compression of small files in multiple cgroups
with memory pressure. Run prepare() then do_test for 6 times:
Before:
real 0m7.762s user 0m11.340s sys 3m11.224s
real 0m8.123s user 0m11.548s sys 3m2.549s
real 0m7.736s user 0m11.515s sys 3m11.171s
real 0m8.539s user 0m11.508s sys 3m7.618s
real 0m7.928s user 0m11.349s sys 3m13.063s
real 0m8.105s user 0m11.128s sys 3m14.313s
After this commit (about ~15% faster):
real 0m6.953s user 0m11.327s sys 2m42.912s
real 0m7.453s user 0m11.343s sys 2m51.942s
real 0m6.916s user 0m11.269s sys 2m43.957s
real 0m6.894s user 0m11.528s sys 2m45.346s
real 0m6.911s user 0m11.095s sys 2m43.168s
real 0m6.773s user 0m11.518s sys 2m40.774s
Link: https://lkml.kernel.org/r/20241104175257.60853-6-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently, there is a lot of code for detecting reparent racing using
kmemcg_id as the synchronization flag. And an intermediate table is
required to record and compare the kmemcg_id.
We can simplify this by just checking the cgroup css status, skip if
cgroup is being offlined. On the reparenting side, ensure no more
allocation is on going and no further allocation will occur by using the
XArray lock as barrier.
Combined with a O(n^2) top-down walk for the allocation, we get rid of the
intermediate table allocation completely. Despite being O(n^2), it should
be actually faster because it's not practical to have a very deep cgroup
level, and in most cases the parent cgroup should have been allocated
already.
This also avoided changing kmemcg_id before reparenting, making cgroups
have a stable index for list_lru_memcg. After this change it's possible
that a dying cgroup will see a NULL value in XArray corresponding to the
kmemcg_id, because the kmemcg_id will point to an empty slot. In such
case, just fallback to use its parent.
As a result the code is simpler, following test also showed a very slight
performance gain (12 test runs):
prepare() {
mkdir /tmp/test-fs
modprobe brd rd_nr=1 rd_size=16777216
mkfs.xfs -f /dev/ram0
mount -t xfs /dev/ram0 /tmp/test-fs
for i in $(seq 10000); do
seq 8000 > "/tmp/test-fs/$i"
done
mkdir -p /sys/fs/cgroup/system.slice/bench/test/1
echo +memory > /sys/fs/cgroup/system.slice/bench/cgroup.subtree_control
echo +memory > /sys/fs/cgroup/system.slice/bench/test/cgroup.subtree_control
echo +memory > /sys/fs/cgroup/system.slice/bench/test/1/cgroup.subtree_control
echo 768M > /sys/fs/cgroup/system.slice/bench/memory.max
}
do_test() {
read_worker() {
mkdir -p "/sys/fs/cgroup/system.slice/bench/test/1/$1"
echo $BASHPID > "/sys/fs/cgroup/system.slice/bench/test/1/$1/cgroup.procs"
read -r __TMP < "/tmp/test-fs/$1";
}
read_in_all() {
for i in $(seq 10000); do
read_worker "$i" &
done; wait
}
echo 3 > /proc/sys/vm/drop_caches
time read_in_all
for i in $(seq 1 10000); do
rmdir "/sys/fs/cgroup/system.slice/bench/test/1/$i" &>/dev/null
done
}
Before:
real 0m3.498s user 0m11.037s sys 0m35.872s
real 1m33.860s user 0m11.593s sys 3m1.169s
real 1m31.883s user 0m11.265s sys 2m59.198s
real 1m32.394s user 0m11.294s sys 3m1.616s
real 1m31.017s user 0m11.379s sys 3m1.349s
real 1m31.931s user 0m11.295s sys 2m59.863s
real 1m32.758s user 0m11.254s sys 2m59.538s
real 1m35.198s user 0m11.145s sys 3m1.123s
real 1m30.531s user 0m11.393s sys 2m58.089s
real 1m31.142s user 0m11.333s sys 3m0.549s
After:
real 0m3.489s user 0m10.943s sys 0m36.036s
real 1m10.893s user 0m11.495s sys 2m38.545s
real 1m29.129s user 0m11.382s sys 3m1.601s
real 1m29.944s user 0m11.494s sys 3m1.575s
real 1m31.208s user 0m11.451s sys 2m59.693s
real 1m25.944s user 0m11.327s sys 2m56.394s
real 1m28.599s user 0m11.312s sys 3m0.162s
real 1m26.746s user 0m11.538s sys 2m55.462s
real 1m30.668s user 0m11.475s sys 3m2.075s
real 1m29.258s user 0m11.292s sys 3m0.780s
Which is slightly faster in real time.
Link: https://lkml.kernel.org/r/20241104175257.60853-5-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
This incorporates Yosry's suggestions in [1] for further simplifying
zswap_store_page(). If the page is successfully compressed and added to
the xarray, we get the pool/objcg refs, and initialize all the entry's
members. Only after this, we add it to the zswap LRU.
In the time between the entry's addition to the xarray and it's member
initialization, we are protected against concurrent stores/loads/swapoff
through the folio lock, and are protected against writeback because the
entry is not on the LRU yet.
This way, we don't have to drop the pool/objcg refs, now that the entry
initialization is centralized to the successful page store code path.
zswap_compress() is modified to take a zswap_pool parameter in keeping
with this simplification (as against obtaining this from entry->pool).
[1]: https://lore.kernel.org/all/CAJD7tkZh6ufHQef5HjXf_F5b5LC1EATexgseD=4WvrO+a6Ni6w@mail.gmail.com/
Link: https://lkml.kernel.org/r/20241002173329.213722-1-kanchana.p.sridhar@intel.com
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Wajdi Feghali <wajdi.k.feghali@intel.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
This series enables zswap_store() to accept and store large folios. The
most significant contribution in this series is from the earlier RFC
submitted by Ryan Roberts [1]. Ryan's original RFC has been migrated to
mm-unstable as of 9-30-2024 in patch 6 of this series, and adapted based
on code review comments received for the current patch-series.
[1]: [RFC PATCH v1] mm: zswap: Store large folios without splitting
https://lore.kernel.org/linux-mm/20231019110543.3284654-1-ryan.roberts@arm.com/T/#u
The first few patches do the prep work for supporting large folios in
zswap_store. Patch 6 provides the main functionality to swap-out large
folios in zswap. Patch 7 adds sysfs per-order hugepages "zswpout"
counters that get incremented upon successful zswap_store of large folios,
and also updates the documentation for this:
/sys/kernel/mm/transparent_hugepage/hugepages-*kB/stats/zswpout
This series is a pre-requisite for zswap compress batching of large folio
swap-out and decompress batching of swap-ins based on swapin_readahead(),
using Intel IAA hardware acceleration, which we would like to submit in
subsequent patch-series, with performance improvement data.
Thanks to Ying Huang for pre-posting review feedback and suggestions!
Thanks also to Nhat, Yosry, Johannes, Barry, Chengming, Usama, Ying and
Matthew for their helpful feedback, code/data reviews and suggestions!
I would like to thank Ryan Roberts for his original RFC [1].
System setup for testing:
=========================
Testing of this series was done with mm-unstable as of 9-27-2024, commit
de2fbaa6d9c3576ec7133ed02a370ec9376bf000 (without this patch-series) and
mm-unstable 9-30-2024 commit c121617e3606be6575cdacfdb63cc8d67b46a568
(with this patch-series). Data was gathered on an Intel Sapphire Rapids
server, dual-socket 56 cores per socket, 4 IAA devices per socket, 503 GiB
RAM and 525G SSD disk partition swap. Core frequency was fixed at
2500MHz.
The vm-scalability "usemem" test was run in a cgroup whose memory.high was
fixed at 150G. The is no swap limit set for the cgroup. 30 usemem
processes were run, each allocating and writing 10G of memory, and
sleeping for 10 sec before exiting:
usemem --init-time -w -O -s 10 -n 30 10g
Other kernel configuration parameters:
zswap compressors : zstd, deflate-iaa
zswap allocator : zsmalloc
vm.page-cluster : 2
In the experiments where "deflate-iaa" is used as the zswap compressor,
IAA "compression verification" is enabled by default (cat
/sys/bus/dsa/drivers/crypto/verify_compress). Hence each IAA compression
will be decompressed internally by the "iaa_crypto" driver, the crc-s
returned by the hardware will be compared and errors reported in case of
mismatches. Thus "deflate-iaa" helps ensure better data integrity as
compared to the software compressors, and the experimental data listed
below is with verify_compress set to "1".
Metrics reporting methodology:
==============================
Total and average throughput are derived from the individual 30 processes'
throughputs reported by usemem. elapsed/sys times are measured with perf.
All percentage changes are "new" vs. "old"; hence a positive value
denotes an increase in the metric, whether it is throughput or latency,
and a negative value denotes a reduction in the metric. Positive
throughput change percentages and negative latency change percentages
denote improvements.
The vm stats and sysfs hugepages stats included with the performance data
provide details on the swapout activity to zswap/swap device.
Testing labels used in data summaries:
======================================
The data refers to these test configurations and the before/after
comparisons that they do:
before-case1:
-------------
mm-unstable 9-27-2024, CONFIG_THP_SWAP=N (compares zswap 4K vs. zswap 64K)
In this scenario, CONFIG_THP_SWAP=N results in 64K/2M folios to be split
into 4K folios that get processed by zswap.
before-case2:
-------------
mm-unstable 9-27-2024, CONFIG_THP_SWAP=Y (compares SSD swap large folios vs. zswap large folios)
In this scenario, CONFIG_THP_SWAP=Y results in zswap rejecting large
folios, which will then be stored by the SSD swap device.
after:
------
v10 of this patch-series, CONFIG_THP_SWAP=Y
The "after" is CONFIG_THP_SWAP=Y and v10 of this patch-series, that results
in 64K/2M folios to not be split, and to be processed by zswap_store.
Regression Testing:
===================
I ran vm-scalability usemem without large folios, i.e., only 4K folios with
mm-unstable and this patch-series. The main goal was to make sure that
there is no functional or performance regression wrt the earlier zswap
behavior for 4K folios, now that 4K folios will be processed by the new
zswap_store() code.
The data indicates there is no significant regression.
-------------------------------------------------------------------------------
4K folios:
==========
zswap compressor zstd zstd zstd zstd v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 4,793,363 4,880,978 4,853,074 1% -1%
Average throughput (KB/s) 159,778 162,699 161,769 1% -1%
elapsed time (sec) 130.14 123.17 126.29 -3% 3%
sys time (sec) 3,135.53 2,985.64 3,083.18 -2% 3%
memcg_high 446,826 444,626 452,930
memcg_swap_fail 0 0 0
zswpout 48,932,107 48,931,971 48,931,820
zswpin 383 386 397
pswpout 0 0 0
pswpin 0 0 0
thp_swpout 0 0 0
thp_swpout_fallback 0 0 0
64kB-mthp_swpout_fallback 0 0 0
pgmajfault 3,063 3,077 3,479
swap_ra 93 94 96
swap_ra_hit 47 47 50
ZSWPOUT-64kB n/a n/a 0
SWPOUT-64kB 0 0 0
-------------------------------------------------------------------------------
Performance Testing:
====================
We list the data for 64K folios with before/after data per-compressor,
followed by the same for 2M pmd-mappable folios.
-------------------------------------------------------------------------------
64K folios: zstd:
=================
zswap compressor zstd zstd zstd zstd v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 5,222,213 1,076,611 6,159,776 18% 472%
Average throughput (KB/s) 174,073 35,887 205,325 18% 472%
elapsed time (sec) 120.50 347.16 108.33 -10% -69%
sys time (sec) 2,930.33 248.16 2,549.65 -13% 927%
memcg_high 416,773 552,200 465,874
memcg_swap_fail 3,192,906 1,293 1,012
zswpout 48,931,583 20,903 48,931,218
zswpin 384 363 410
pswpout 0 40,778,448 0
pswpin 0 16 0
thp_swpout 0 0 0
thp_swpout_fallback 0 0 0
64kB-mthp_swpout_fallback 3,192,906 1,293 1,012
pgmajfault 3,452 3,072 3,061
swap_ra 90 87 107
swap_ra_hit 42 43 57
ZSWPOUT-64kB n/a n/a 3,057,173
SWPOUT-64kB 0 2,548,653 0
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
64K folios: deflate-iaa:
========================
zswap compressor deflate-iaa deflate-iaa deflate-iaa deflate-iaa v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 5,652,608 1,089,180 7,189,778 27% 560%
Average throughput (KB/s) 188,420 36,306 239,659 27% 560%
elapsed time (sec) 102.90 343.35 87.05 -15% -75%
sys time (sec) 2,246.86 213.53 1,864.16 -17% 773%
memcg_high 576,104 502,907 642,083
memcg_swap_fail 4,016,117 1,407 1,478
zswpout 61,163,423 22,444 57,798,716
zswpin 401 368 454
pswpout 0 40,862,080 0
pswpin 0 20 0
thp_swpout 0 0 0
thp_swpout_fallback 0 0 0
64kB-mthp_swpout_fallback 4,016,117 1,407 1,478
pgmajfault 3,063 3,153 3,122
swap_ra 96 93 156
swap_ra_hit 46 45 83
ZSWPOUT-64kB n/a n/a 3,611,032
SWPOUT-64kB 0 2,553,880 0
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
2M folios: zstd:
================
zswap compressor zstd zstd zstd zstd v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 5,895,500 1,109,694 6,484,224 10% 484%
Average throughput (KB/s) 196,516 36,989 216,140 10% 484%
elapsed time (sec) 108.77 334.28 106.33 -2% -68%
sys time (sec) 2,657.14 94.88 2,376.13 -11% 2404%
memcg_high 64,200 66,316 56,898
memcg_swap_fail 101,182 70 27
zswpout 48,931,499 36,507 48,890,640
zswpin 380 379 377
pswpout 0 40,166,400 0
pswpin 0 0 0
thp_swpout 0 78,450 0
thp_swpout_fallback 101,182 70 27
2MB-mthp_swpout_fallback 0 0 27
pgmajfault 3,067 3,417 3,311
swap_ra 91 90 854
swap_ra_hit 45 45 810
ZSWPOUT-2MB n/a n/a 95,459
SWPOUT-2MB 0 78,450 0
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
2M folios: deflate-iaa:
=======================
zswap compressor deflate-iaa deflate-iaa deflate-iaa deflate-iaa v10
before-case1 before-case2 after vs. vs.
case1 case2
-------------------------------------------------------------------------------
Total throughput (KB/s) 6,286,587 1,126,785 7,073,464 13% 528%
Average throughput (KB/s) 209,552 37,559 235,782 13% 528%
elapsed time (sec) 96.19 333.03 85.79 -11% -74%
sys time (sec) 2,141.44 99.96 1,826.67 -15% 1727%
memcg_high 99,253 64,666 79,718
memcg_swap_fail 129,074 53 165
zswpout 61,312,794 28,321 56,045,120
zswpin 383 406 403
pswpout 0 40,048,128 0
pswpin 0 0 0
thp_swpout 0 78,219 0
thp_swpout_fallback 129,074 53 165
2MB-mthp_swpout_fallback 0 0 165
pgmajfault 3,430 3,077 31,468
swap_ra 91 103 84,373
swap_ra_hit 47 46 84,317
ZSWPOUT-2MB n/a n/a 109,229
SWPOUT-2MB 0 78,219 0
-------------------------------------------------------------------------------
And finally, this is a comparison of deflate-iaa vs. zstd with v10 of this
patch-series:
---------------------------------------------
zswap_store large folios v10
Impr w/ deflate-iaa vs. zstd
64K folios 2M folios
---------------------------------------------
Throughput (KB/s) 17% 9%
elapsed time (sec) -20% -19%
sys time (sec) -27% -23%
---------------------------------------------
Conclusions based on the performance results:
=============================================
v10 wrt before-case1:
---------------------
We see significant improvements in throughput, elapsed and sys time for
zstd and deflate-iaa, when comparing before-case1 (THP_SWAP=N) vs. after
(THP_SWAP=Y) with zswap_store large folios.
v10 wrt before-case2:
---------------------
We see even more significant improvements in throughput and elapsed time
for zstd and deflate-iaa, when comparing before-case2 (large-folio-SSD)
vs. after (large-folio-zswap). The sys time increases with
large-folio-zswap as expected, due to the CPU compression time
vs. asynchronous disk write times, as pointed out by Ying and Yosry.
In before-case2, when zswap does not store large folios, only allocations
and cgroup charging due to 4K folio zswap stores count towards the cgroup
memory limit. However, in the after scenario, with the introduction of
zswap_store() of large folios, there is an added component of the zswap
compressed pool usage from large folio stores from potentially all 30
processes, that gets counted towards the memory limit. As a result, we see
higher swapout activity in the "after" data.
Summary:
========
The v10 data presented above shows that zswap_store of large folios
demonstrates good throughput/performance improvements compared to
conventional SSD swap of large folios with a sufficiently large 525G SSD
swap device. Hence, it seems reasonable for zswap_store to support large
folios, so that further performance improvements can be implemented.
In the experimental setup used in this patchset, we have enabled IAA
compress verification to ensure additional hardware data integrity CRC
checks not currently done by the software compressors. We see good
throughput/latency improvements with deflate-iaa vs. zstd with zswap_store
of large folios.
Some of the ideas for further reducing latency that have shown promise in
our experiments, are:
1) IAA compress/decompress batching.
2) Distributing compress jobs across all IAA devices on the socket.
The tests run for this patchset are using only 1 IAA device per core, that
avails of 2 compress engines on the device. In our experiments with IAA
batching, we distribute compress jobs from all cores to the 8 compress
engines available per socket. We further compress the pages in each folio
in parallel in the accelerator. As a result, we improve compress latency
and reclaim throughput.
In decompress batching, we use swapin_readahead to generate a prefetch
batch of 4K folios that we decompress in parallel in IAA.
------------------------------------------------------------------------------
IAA compress/decompress batching
Further improvements wrt v10 zswap_store Sequential
subpage store using "deflate-iaa":
"deflate-iaa" Batching "deflate-iaa-canned" [2] Batching
Additional Impr Additional Impr
64K folios 2M folios 64K folios 2M folios
------------------------------------------------------------------------------
Throughput (KB/s) 19% 43% 26% 55%
elapsed time (sec) -5% -14% -10% -21%
sys time (sec) 4% -7% -4% -18%
------------------------------------------------------------------------------
With zswap IAA compress/decompress batching, we are able to demonstrate
significant performance improvements and memory savings in server
scalability experiments in highly contended system scenarios under
significant memory pressure; as compared to software compressors. We hope
to submit this work in subsequent patch series. The current patch-series
is a prequisite for these future submissions.
This patch (of 7):
zswap_store() will store large folios by compressing them page by page.
This patch provides a sequential implementation of storing a large folio
in zswap_store() by iterating through each page in the folio to compress
and store it in the zswap zpool.
zswap_store() calls the newly added zswap_store_page() function for each
page in the folio. zswap_store_page() handles compressing and storing
each page.
We check the global and per-cgroup limits once at the beginning of
zswap_store(), and only check that the limit is not reached yet. This is
racy and inaccurate, but it should be sufficient for now. We also obtain
initial references to the relevant objcg and pool to guarantee that
subsequent references can be acquired by zswap_store_page(). A new
function zswap_pool_get() is added to facilitate this.
If these one-time checks pass, we compress the pages of the folio, while
maintaining a running count of compressed bytes for all the folio's pages.
If all pages are successfully compressed and stored, we do the cgroup
zswap charging with the total compressed bytes, and batch update the
zswap_stored_pages atomic/zswpout event stats with folio_nr_pages() once,
before returning from zswap_store().
If an error is encountered during the store of any page in the folio, all
pages in that folio currently stored in zswap will be invalidated. Thus,
a folio is either entirely stored in zswap, or entirely not stored in
zswap.
The most important value provided by this patch is it enables swapping out
large folios to zswap without splitting them. Furthermore, it batches
some operations while doing so (cgroup charging, stats updates).
This patch also forms the basis for building compress batching of pages in
a large folio in zswap_store() by compressing up to say, 8 pages of the
folio in parallel in hardware using the Intel In-Memory Analytics
Accelerator (Intel IAA).
This change reuses and adapts the functionality in Ryan Roberts' RFC
patch [1]:
"[RFC,v1] mm: zswap: Store large folios without splitting"
[1] https://lore.kernel.org/linux-mm/20231019110543.3284654-1-ryan.roberts@arm.com/T/#u
Link: https://lkml.kernel.org/r/20241001053222.6944-1-kanchana.p.sridhar@intel.com
Link: https://lkml.kernel.org/r/20241001053222.6944-7-kanchana.p.sridhar@intel.com
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Originally-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Wajdi Feghali <wajdi.k.feghali@intel.com>
Cc: "Zou, Nanhai" <nanhai.zou@intel.com>
Cc: Barry Song <21cnbao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
For zswap_store() to support large folios, we need to be able to do a
batch update of zswap_stored_pages upon successful store of all pages in
the folio. For this, we need to add folio_nr_pages(), which returns a
long, to zswap_stored_pages.
Link: https://lkml.kernel.org/r/20241001053222.6944-6-kanchana.p.sridhar@intel.com
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Wajdi Feghali <wajdi.k.feghali@intel.com>
Cc: "Zou, Nanhai" <nanhai.zou@intel.com>
Cc: Barry Song <21cnbao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Modify the name of the existing zswap_pool_get() to zswap_pool_tryget() to
be representative of the call it makes to percpu_ref_tryget(). A
subsequent patch will introduce a new zswap_pool_get() that calls
percpu_ref_get().
The intent behind this change is for higher level zswap API such as
zswap_store() to call zswap_pool_tryget() to check upfront if the pool's
refcount is "0" (which means it could be getting destroyed) and to handle
this as an error condition. zswap_store() would proceed only if
zswap_pool_tryget() returns success, and any additional pool refcounts
that need to be obtained for compressing sub-pages in a large folio could
simply call zswap_pool_get().
Link: https://lkml.kernel.org/r/20241001053222.6944-4-kanchana.p.sridhar@intel.com
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Wajdi Feghali <wajdi.k.feghali@intel.com>
Cc: "Zou, Nanhai" <nanhai.zou@intel.com>
Cc: Barry Song <21cnbao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
For zswap_store() to be able to store a large folio by compressing it one
page at a time, zswap_compress() needs to accept a page as input. This
will allow us to iterate through each page in the folio in zswap_store(),
compress it and store it in the zpool.
Link: https://lkml.kernel.org/r/20241001053222.6944-3-kanchana.p.sridhar@intel.com
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Wajdi Feghali <wajdi.k.feghali@intel.com>
Cc: "Zou, Nanhai" <nanhai.zou@intel.com>
Cc: Barry Song <21cnbao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Pick up e7ac4daeed91 ("mm: count zeromap read and set for swapout and
swapin") in order to move
mm: define obj_cgroup_get() if CONFIG_MEMCG is not defined
mm: zswap: modify zswap_compress() to accept a page instead of a folio
mm: zswap: rename zswap_pool_get() to zswap_pool_tryget()
mm: zswap: modify zswap_stored_pages to be atomic_long_t
mm: zswap: support large folios in zswap_store()
mm: swap: count successful large folio zswap stores in hugepage zswpout stats
mm: zswap: zswap_store_page() will initialize entry after adding to xarray.
mm: add per-order mTHP swpin counters
from mm-unstable into mm-stable.
|
|
When the proportion of folios from the zeromap is small, missing their
accounting may not significantly impact profiling. However, it's easy to
construct a scenario where this becomes an issue—for example, allocating
1 GB of memory, writing zeros from userspace, followed by MADV_PAGEOUT,
and then swapping it back in. In this case, the swap-out and swap-in
counts seem to vanish into a black hole, potentially causing semantic
ambiguity.
On the other hand, Usama reported that zero-filled pages can exceed 10% in
workloads utilizing zswap, while Hailong noted that some app in Android
have more than 6% zero-filled pages. Before commit 0ca0c24e3211 ("mm:
store zero pages to be swapped out in a bitmap"), both zswap and zRAM
implemented similar optimizations, leading to these optimized-out pages
being counted in either zswap or zRAM counters (with pswpin/pswpout also
increasing for zRAM). With zeromap functioning prior to both zswap and
zRAM, userspace will no longer detect these swap-out and swap-in actions.
We have three ways to address this:
1. Introduce a dedicated counter specifically for the zeromap.
2. Use pswpin/pswpout accounting, treating the zero map as a standard
backend. This approach aligns with zRAM's current handling of
same-page fills at the device level. However, it would mean losing the
optimized-out page counters previously available in zRAM and would not
align with systems using zswap. Additionally, as noted by Nhat Pham,
pswpin/pswpout counters apply only to I/O done directly to the backend
device.
3. Count zeromap pages under zswap, aligning with system behavior when
zswap is enabled. However, this would not be consistent with zRAM, nor
would it align with systems lacking both zswap and zRAM.
Given the complications with options 2 and 3, this patch selects
option 1.
We can find these counters from /proc/vmstat (counters for the whole
system) and memcg's memory.stat (counters for the interested memcg).
For example:
$ grep -E 'swpin_zero|swpout_zero' /proc/vmstat
swpin_zero 1648
swpout_zero 33536
$ grep -E 'swpin_zero|swpout_zero' /sys/fs/cgroup/system.slice/memory.stat
swpin_zero 3905
swpout_zero 3985
This patch does not address any specific zeromap bug, but the missing
swpout and swpin counts for zero-filled pages can be highly confusing and
may mislead user-space agents that rely on changes in these counters as
indicators. Therefore, we add a Fixes tag to encourage the inclusion of
this counter in any kernel versions with zeromap.
Many thanks to Kanchana for the contribution of changing
count_objcg_event() to count_objcg_events() to support large folios[1],
which has now been incorporated into this patch.
[1] https://lkml.kernel.org/r/20241001053222.6944-5-kanchana.p.sridhar@intel.com
Link: https://lkml.kernel.org/r/20241107011246.59137-1-21cnbao@gmail.com
Fixes: 0ca0c24e3211 ("mm: store zero pages to be swapped out in a bitmap")
Co-developed-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Hailong Liu <hailong.liu@oppo.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
zswap_invalidation simply calls xa_erase, which acquires the Xarray lock
first, then does a look up. This has a higher overhead even if zswap is
not used or the tree is empty.
So instead, do a very lightweight xa_empty check first, if there is
nothing to erase, don't touch the lock or the tree.
Using xa_empty rather than zswap_never_enabled is more helpful as it cover
both case where zswap wes never used or the particular range doesn't have
any zswap entry. And it's safe as the swap slot should be currently
pinned by caller with HAS_CACHE.
Sequential SWAP in/out tests with zswap disabled showed a minor
performance gain, SWAP in of zero page with zswap enabled also showed a
performance gain. (swapout is basically unchanged so only test one case):
Swapout of 2G zero page using brd as SWAP, zswap disabled
(total time, 4 testrun, +0.1%):
Before: 1705013 us 1703119 us 1704335 us 1705848 us.
After: 1703579 us 1710640 us 1703625 us 1708699 us.
Swapin of 2G zero page using brd as SWAP, zswap disabled
(total time, 4 testrun, -3.5%):
Before: 1912312 us 1915692 us 1905837 us 1912706 us.
After: 1845354 us 1849691 us 1845868 us 1841828 us.
Swapin of 2G zero page using brd as SWAP, zswap enabled
(total time, 4 testrun, -3.3%):
Before: 1897994 us 1894681 us 1899982 us 1898333 us
After: 1835894 us 1834113 us 1832047 us 1833125 us
Swapin of 2G random page using brd as SWAP, zswap enabled
(total time, 4 testrun, -0.1%):
Before: 4519747 us 4431078 us 4430185 us 4439999 us
After: 4492176 us 4437796 us 4434612 us 4434289 us
And the performance is very slightly better or unchanged for
build kernel test with zswap enabled or disabled.
Build Linux Kernel with defconfig and -j32 in 1G memory cgroup,
using brd SWAP, zswap disabled (sys time in seconds, 6 testrun, -0.1%):
Before: 1648.83 1653.52 1666.34 1665.95 1663.06 1656.67
After: 1651.36 1661.89 1645.70 1657.45 1662.07 1652.83
Build Linux Kernel with defconfig and -j32 in 2G memory cgroup,
using brd SWAP zswap enabled (sys time in seconds, 6 testrun, -0.3%):
Before: 1240.25 1254.06 1246.77 1265.92 1244.23 1227.74
After: 1226.41 1218.21 1249.12 1249.13 1244.39 1233.01
Link: https://lkml.kernel.org/r/20241011171950.62684-1-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Made a minor edit in the comments for 'struct zswap_entry' to delete the
description of the 'value' member that was deleted in commit 20a5532ffa53
("mm: remove code to handle same filled pages").
Link: https://lkml.kernel.org/r/20241002194213.30041-1-kanchana.p.sridhar@intel.com
Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Fixes: 20a5532ffa53 ("mm: remove code to handle same filled pages")
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Usama Arif <usamaarif642@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Wajdi Feghali <wajdi.k.feghali@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
With an earlier commit to handle zero-filled pages in swap directly, and
with only 1% of the same-filled pages being non-zero, zswap no longer
needs to handle same-filled pages and can just work on compressed pages.
Link: https://lkml.kernel.org/r/20240823190545.979059-3-usamaarif642@gmail.com
Signed-off-by: Usama Arif <usamaarif642@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "improving dynamic zswap shrinker protection scheme", v3.
When experimenting with the memory-pressure based (i.e "dynamic") zswap
shrinker in production, we observed a sharp increase in the number of
swapins, which led to performance regression. We were able to trace this
regression to the following problems with the shrinker's warm pages
protection scheme:
1. The protection decays way too rapidly, and the decaying is coupled with
zswap stores, leading to anomalous patterns, in which a small batch of
zswap stores effectively erase all the protection in place for the
warmer pages in the zswap LRU.
This observation has also been corroborated upstream by Takero Funaki
(in [1]).
2. We inaccurately track the number of swapped in pages, missing the
non-pivot pages that are part of the readahead window, while counting
the pages that are found in the zswap pool.
To alleviate these two issues, this patch series improve the dynamic zswap
shrinker in the following manner:
1. Replace the protection size tracking scheme with a second chance
algorithm. This new scheme removes the need for haphazard stats
decaying, and automatically adjusts the pace of pages aging with memory
pressure, and writeback rate with pool activities: slowing down when
the pool is dominated with zswpouts, and speeding up when the pool is
dominated with stale entries.
2. Fix the tracking of the number of swapins to take into account
non-pivot pages in the readahead window.
With these two changes in place, in a kernel-building benchmark without
any cold data added, the number of swapins is reduced by 64.12%. This
translate to a 10.32% reduction in build time. We also observe a 3%
reduction in kernel CPU time.
In another benchmark, with cold data added (to gauge the new algorithm's
ability to offload cold data), the new second chance scheme outperforms
the old protection scheme by around 0.7%, and actually written back around
21% more pages to backing swap device. So the new scheme is just as good,
if not even better than the old scheme on this front as well.
[1]: https://lore.kernel.org/linux-mm/CAPpodddcGsK=0Xczfuk8usgZ47xeyf4ZjiofdT+ujiyz6V2pFQ@mail.gmail.com/
This patch (of 2):
Current zswap shrinker's heuristics to prevent overshrinking is brittle
and inaccurate, specifically in the way we decay the protection size (i.e
making pages in the zswap LRU eligible for reclaim).
We currently decay protection aggressively in zswap_lru_add() calls. This
leads to the following unfortunate effect: when a new batch of pages enter
zswap, the protection size rapidly decays to below 25% of the zswap LRU
size, which is way too low.
We have observed this effect in production, when experimenting with the
zswap shrinker: the rate of shrinking shoots up massively right after a
new batch of zswap stores. This is somewhat the opposite of what we want
originally - when new pages enter zswap, we want to protect both these new
pages AND the pages that are already protected in the zswap LRU.
Replace existing heuristics with a second chance algorithm
1. When a new zswap entry is stored in the zswap pool, its referenced
bit is set.
2. When the zswap shrinker encounters a zswap entry with the referenced
bit set, give it a second chance - only flips the referenced bit and
rotate it in the LRU.
3. If the shrinker encounters the entry again, this time with its
referenced bit unset, then it can reclaim the entry.
In this manner, the aging of the pages in the zswap LRUs are decoupled
from zswap stores, and picks up the pace with increasing memory pressure
(which is what we want).
The second chance scheme allows us to modulate the writeback rate based on
recent pool activities. Entries that recently entered the pool will be
protected, so if the pool is dominated by such entries the writeback rate
will reduce proportionally, protecting the workload's workingset.On the
other hand, stale entries will be written back quickly, which increases
the effective writeback rate.
The referenced bit is added at the hole after the `length` field of struct
zswap_entry, so there is no extra space overhead for this algorithm.
We will still maintain the count of swapins, which is consumed and
subtracted from the lru size in zswap_shrinker_count(), to further
penalize past overshrinking that led to disk swapins. The idea is that
had we considered this many more pages in the LRU active/protected, they
would not have been written back and we would not have had to swapped them
in.
To test this new heuristics, I built the kernel under a cgroup with
memory.max set to 2G, on a host with 36 cores:
With the old shrinker:
real: 263.89s
user: 4318.11s
sys: 673.29s
swapins: 227300.5
With the second chance algorithm:
real: 244.85s
user: 4327.22s
sys: 664.39s
swapins: 94663
(average over 5 runs)
We observe an 1.3% reduction in kernel CPU usage, and around 7.2%
reduction in real time. Note that the number of swapped in pages
dropped by 58%.
[nphamcs@gmail.com: fix a small mistake in the referenced bit documentation]
Link: https://lkml.kernel.org/r/20240806003403.3142387-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20240805232243.2896283-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20240805232243.2896283-2-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Takero Funaki <flintglass@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
This patch fixes the zswap global shrinker, which did not shrink the zpool
as expected.
The issue addressed is that shrink_worker() did not distinguish between
unexpected errors and expected errors, such as failed writeback from an
empty memcg. The shrinker would stop shrinking after iterating through
the memcg tree 16 times, even if there was only one empty memcg.
With this patch, the shrinker no longer considers encountering an empty
memcg, encountering a memcg with writeback disabled, or reaching the end
of a memcg tree walk as a failure, as long as there are memcgs that are
candidates for writeback. Systems with one or more empty memcgs will now
observe significantly higher zswap writeback activity after the zswap pool
limit is hit.
To avoid an infinite loop when there are no writeback candidates, this
patch tracks writeback attempts during memcg tree walks and limits reties
if no writeback candidates are found.
To handle the empty memcg case, the helper function shrink_memcg() is
modified to check if the memcg is empty and then return -ENOENT.
Link: https://lkml.kernel.org/r/20240731004918.33182-3-flintglass@gmail.com
Fixes: a65b0e7607cc ("zswap: make shrinking memcg-aware")
Signed-off-by: Takero Funaki <flintglass@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm: zswap: fixes for global shrinker", v5.
This series addresses issues in the zswap global shrinker that could not
shrink stored pages. With this series, the shrinker continues to shrink
pages until it reaches the accept threshold more reliably, gives much
higher writeback when the zswap pool limit is hit.
This patch (of 2):
This patch fixes an issue where the zswap global shrinker stopped
iterating through the memcg tree.
The problem was that shrink_worker() would restart iterating memcg tree
from the tree root, considering an offline memcg as a failure, and abort
shrinking after encountering the same offline memcg 16 times even if there
is only one offline memcg. After this change, an offline memcg in the
tree is no longer considered a failure. This allows the shrinker to
continue shrinking the other online memcgs regardless of whether an
offline memcg exists, gives higher zswap writeback activity.
To avoid holding refcount of offline memcg encountered during the memcg
tree walking, shrink_worker() must continue iterating to release the
offline memcg to ensure the next memcg stored in the cursor is online.
The offline memcg cleaner has also been changed to avoid the same issue.
When the next memcg of the offlined memcg is also offline, the refcount
stored in the iteration cursor was held until the next shrink_worker()
run. The cleaner must release the offline memcg recursively.
[yosryahmed@google.com: make critical section more obvious, unify comments]
Link: https://lkml.kernel.org/r/CAJD7tkaScz+SbB90Q1d5mMD70UfM2a-J2zhXDT9sePR7Qap45Q@mail.gmail.com
Link: https://lkml.kernel.org/r/20240731004918.33182-1-flintglass@gmail.com
Link: https://lkml.kernel.org/r/20240731004918.33182-2-flintglass@gmail.com
Fixes: a65b0e7607cc ("zswap: make shrinking memcg-aware")
Signed-off-by: Takero Funaki <flintglass@gmail.com>
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
We accidentally deleted a tab in commit f84152e9efc5 ("mm/zswap: use only
one pool in zswap"). Add it back.
Link: https://lkml.kernel.org/r/c15066a0-f061-42c9-b0f5-d60281d3d5d8@stanley.mountain
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Zswap uses 32 pools to workaround the locking scalability problem in zswap
backends (mainly zsmalloc nowadays), which brings its own problems like
memory waste and more memory fragmentation.
Testing results show that we can have near performance with only one pool
in zswap after changing zsmalloc to use per-size_class lock instead of
pool spinlock.
Testing kernel build (make bzImage -j32) on tmpfs with memory.max=1GB, and
zswap shrinker enabled with 10GB swapfile on ext4.
real user sys
6.10.0-rc3 138.18 1241.38 1452.73
6.10.0-rc3-onepool 149.45 1240.45 1844.69
6.10.0-rc3-onepool-perclass 138.23 1242.37 1469.71
And do the same testing using zbud, which shows a little worse performance
as expected since we don't do any locking optimization for zbud. I think
it's acceptable since zsmalloc became a lot more popular than other
backends, and we may want to support only zsmalloc in the future.
real user sys
6.10.0-rc3-zbud 138.23 1239.58 1430.09
6.10.0-rc3-onepool-zbud 139.64 1241.37 1516.59
[chengming.zhou@linux.dev: fix error handling in zswap_pool_create(), per Dan Carpenter]
Link: https://lkml.kernel.org/r/20240621-zsmalloc-lock-mm-everything-v2-2-d30e9cd2b793@linux.dev
[chengming.zhou@linux.dev: fix error handling again in zswap_pool_create(), per Yosry]
Link: https://lkml.kernel.org/r/20240625-zsmalloc-lock-mm-everything-v3-2-ad941699cb61@linux.dev
Link: https://lkml.kernel.org/r/20240617-zsmalloc-lock-mm-everything-v1-2-5e5081ea11b3@linux.dev
Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Zswap does not support storing or loading large folios. Until proper
support is added, attempts to load large folios from zswap are a bug.
For example, if a swapin fault observes that contiguous PTEs are pointing
to contiguous swap entries and tries to swap them in as a large folio,
swap_read_folio() will pass in a large folio to zswap_load(), but
zswap_load() will only effectively load the first page in the folio. If
the first page is not in zswap, the folio will be read from disk, even
though other pages may be in zswap.
In both cases, this will lead to silent data corruption. Proper support
needs to be added before large folio swapins and zswap can work together.
Looking at callers of swap_read_folio(), it seems like they are either
allocated from __read_swap_cache_async() or do_swap_page() in the
SWP_SYNCHRONOUS_IO path. Both of which allocate order-0 folios, so
everything is fine for now.
However, there is ongoing work to add to support large folio swapins [1].
To make sure new development does not break zswap (or get broken by
zswap), add minimal handling of incorrect loads of large folios to zswap.
First, move the call folio_mark_uptodate() inside zswap_load().
If a large folio load is attempted, and zswap was ever enabled on the
system, return 'true' without calling folio_mark_uptodate(). This will
prevent the folio from being read from disk, and will emit an IO error
because the folio is not uptodate (e.g. do_swap_fault() will return
VM_FAULT_SIGBUS). It may not be reliable recovery in all cases, but it is
better than nothing.
This was tested by hacking the allocation in __read_swap_cache_async() to
use order 2 and __GFP_COMP.
In the future, to handle this correctly, the swapin code should:
(a) Fall back to order-0 swapins if zswap was ever used on the
machine, because compressed pages remain in zswap after it is
disabled.
(b) Add proper support to swapin large folios from zswap (fully or
partially).
Probably start with (a) then followup with (b).
[1]https://lore.kernel.org/linux-mm/20240304081348.197341-6-21cnbao@gmail.com/
Link: https://lkml.kernel.org/r/20240611024516.1375191-3-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Barry Song <baohua@kernel.org>
Cc: Barry Song <baohua@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Add zswap_never_enabled() to skip the xarray lookup in zswap_load() if
zswap was never enabled on the system. It is implemented using static
branches for efficiency, as enabling zswap should be a rare event. This
could shave some cycles off zswap_load() when CONFIG_ZSWAP is used but
zswap is never enabled.
However, the real motivation behind this patch is two-fold:
- Incoming large folio swapin work will need to fallback to order-0
folios if zswap was ever enabled, because any part of the folio could be
in zswap, until proper handling of large folios with zswap is added.
- A warning and recovery attempt will be added in a following change in
case the above was not done incorrectly. Zswap will fail the read if
the folio is large and it was ever enabled.
Expose zswap_never_enabled() in the header for the swapin work to use
it later.
[yosryahmed@google.com: expose zswap_never_enabled() in the header]
Link: https://lkml.kernel.org/r/Zmjf0Dr8s9xSW41X@google.com
Link: https://lkml.kernel.org/r/20240611024516.1375191-2-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In preparation for introducing a similar function, rename
is_zswap_enabled() to use zswap_* prefix like other zswap functions.
Link: https://lkml.kernel.org/r/20240611024516.1375191-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
A variable name 'page' is used in zswap_is_folio_same_filled() and
zswap_fill_page() to point at the kmapped data in a folio. Use 'data'
instead to avoid confusion and stop it from showing up when searching
for 'page' references in mm/zswap.c.
While we are at it, move the kmap/kunmap calls into zswap_fill_page(),
make it take in a folio, and rename it to zswap_fill_folio().
Link: https://lkml.kernel.org/r/20240524033819.1953587-4-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Eliminate the last explicit 'struct page' reference in mm/zswap.c.
Link: https://lkml.kernel.org/r/20240524033819.1953587-3-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm: zswap: trivial folio conversions".
Some trivial folio conversions in zswap code.
This patch (of 3):
sg_set_folio() is equivalent to sg_set_page() for order-0 folios, which
are the only ones supported by zswap. Now zswap_decompress() can take in
a folio directly.
Link: https://lkml.kernel.org/r/20240524033819.1953587-1-yosryahmed@google.com
Link: https://lkml.kernel.org/r/20240524033819.1953587-2-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
These knobs offer more fine-grained control to userspace than needed and
directly expose/influence kernel implementation; remove them.
For disabling same_filled handling, there is no logical reason to refuse
storing same-filled pages more efficiently and opt for compression.
Scanning pages for patterns may be an argument, but the page contents will
be read into the CPU cache anyway during compression. Also, removing the
same_filled handling code does not move the needle significantly in terms
of performance anyway [1].
For disabling non_same_filled handling, it was added when the compressed
pages in zswap were not being properly charged to memcgs, as workloads
could escape the accounting with compression [2]. This is no longer the
case after commit f4840ccfca25 ("zswap: memcg accounting"), and using
zswap without compression does not make much sense.
[1]https://lore.kernel.org/lkml/CAJD7tkaySFP2hBQw4pnZHJJwe3bMdjJ1t9VC2VJd=khn1_TXvA@mail.gmail.com/
[2]https://lore.kernel.org/lkml/19d5cdee-2868-41bd-83d5-6da75d72e940@maciej.szmigiero.name/
[yosryahmed@google.com: remove same_filled_pages from docs]
Link: https://lkml.kernel.org/r/ZhxFVggdyvCo79jc@google.com
Link: https://lkml.kernel.org/r/20240413022407.785696-5-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently, zswap_store() checks zswap_same_filled_pages_enabled, kmaps the
folio, then calls zswap_is_page_same_filled() to check the folio contents.
Move this logic into zswap_is_page_same_filled() as well (and rename it
to use 'folio' while we are at it).
This makes zswap_store() cleaner, and makes following changes to that
logic contained within the helper.
While we are at it:
- Rename the insert_entry label to store_entry to match xa_store().
- Add comment headers for same-filled functions and the main API
functions (load, store, invalidate, swapon, swapoff).
No functional change intended.
Link: https://lkml.kernel.org/r/20240413022407.785696-4-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Refactor limit and acceptance threshold checking outside of zswap_store().
This code will be moved around in a following patch, so it would be
cleaner to move a function call around.
Link: https://lkml.kernel.org/r/20240413022407.785696-3-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "zswap same-filled and limit checking cleanups", v3.
Miscellaneous cleanups for limit checking and same-filled handling in the
store path. This series was broken out of the "zswap: store zero-filled
pages more efficiently" series [1]. It contains the cleanups and drops
the main functional changes.
[1]https://lore.kernel.org/lkml/20240325235018.2028408-1-yosryahmed@google.com/
This patch (of 4):
The cleanup code in zswap_store() is not pretty, particularly the 'shrink'
label at the bottom that ends up jumping between cleanup labels.
Instead of having a dedicated label to shrink the pool, just use
zswap_pool_reached_full directly to figure out if the pool needs
shrinking. zswap_pool_reached_full should be true if and only if the pool
needs shrinking.
The only caveat is that the value of zswap_pool_reached_full may be
changed by concurrent zswap_store() calls between checking the limit and
testing zswap_pool_reached_full in the cleanup code. This is fine
because:
- If zswap_pool_reached_full was true during limit checking then became
false during the cleanup code, then someone else already took care of
shrinking the pool and there is no need to queue the worker. That
would be a good change.
- If zswap_pool_reached_full was false during limit checking then became
true during the cleanup code, then someone else hit the limit
meanwhile. In this case, both threads will try to queue the worker,
but it never gets queued more than once anyway. Also, calling
queue_work() multiple times when the limit is hit could already happen
today, so this isn't a significant change in any way.
Link: https://lkml.kernel.org/r/20240413022407.785696-1-yosryahmed@google.com
Link: https://lkml.kernel.org/r/20240413022407.785696-2-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Very deep RB tree requires rebalance at times. That contributes to the
zswap fault latencies. Xarray does not need to perform tree rebalance.
Replacing RB tree to xarray can have some small performance gain.
One small difference is that xarray insert might fail with ENOMEM, while
RB tree insert does not allocate additional memory.
The zswap_entry size will reduce a bit due to removing the RB node, which
has two pointers and a color field. Xarray store the pointer in the
xarray tree rather than the zswap_entry. Every entry has one pointer from
the xarray tree. Overall, switching to xarray should save some memory, if
the swap entries are densely packed.
Notice the zswap_rb_search and zswap_rb_insert often followed by
zswap_rb_erase. Use xa_erase and xa_store directly. That saves one tree
lookup as well.
Remove zswap_invalidate_entry due to no need to call zswap_rb_erase any
more. Use zswap_free_entry instead.
The "struct zswap_tree" has been replaced by "struct xarray". The tree
spin lock has transferred to the xarray lock.
Run the kernel build testing 5 times for each version, averages:
(memory.max=2GB, zswap shrinker and writeback enabled, one 50GB swapfile,
24 HT core, 32 jobs)
mm-unstable-4aaccadb5c04 xarray v9
user 3548.902 3534.375
sys 522.232 520.976
real 202.796 200.864
[chrisl@kernel.org: restore original comment "erase" to "invalidate"]
Link: https://lkml.kernel.org/r/20240326-zswap-xarray-v10-1-bf698417c968@kernel.org
Link: https://lkml.kernel.org/r/20240326-zswap-xarray-v9-1-d2891a65dfc7@kernel.org
Signed-off-by: Chris Li <chrisl@kernel.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
nr_stored was introduced by commit b5ba474f3f51 ("zswap: shrink zswap pool
based on memory pressure") as a per zswap_pool counter of the number of
stored pages that are not same-filled pages. It is used in
zswap_shrinker_count() to scale the number of freeable compressed pages by
the compression ratio. That is, to reduce the amount of writeback from
zswap with higher compression ratios as the ROI from IO diminishes.
Later on, commit bf9b7df23cb3 ("mm/zswap: global lru and shrinker shared
by all zswap_pools") made the shrinker global (not per zswap_pool), and
replaced nr_stored with nr_zswap_stored (initially introduced as
zswap.nr_stored), which is now a global counter.
The counter is now awfully close to zswap_stored_pages. The only
difference is that the latter also includes same-filled pages. Also, when
memcgs are enabled, we use memcg_page_state(memcg, MEMCG_ZSWAPPED), which
includes same-filled pages anyway (i.e. equivalent to
zswap_stored_pages).
Use zswap_stored_pages instead in zswap_shrinker_count() to keep things
consistent whether memcgs are enabled or not, and add a comment about the
number of freeable pages possibly being scaled down more than it should if
we have lots of same-filled pages (i.e. inflated compression ratio).
Remove nr_zswap_stored and one atomic operation in the store and free
paths.
Link: https://lkml.kernel.org/r/20240322001001.1562517-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
zswap_find_zpool() checks if ZSWAP_NR_ZPOOLS > 1, which is always true.
This is a remnant from a patch version that had ZSWAP_NR_ZPOOLS as a
config option and never made it upstream. Remove the unnecessary check.
Link: https://lkml.kernel.org/r/20240311235210.2937484-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
All zswap backends track their pool sizes in pages. Currently they
multiply by PAGE_SIZE for zswap, only for zswap to divide again in order
to do limit math. Report pages directly.
Link: https://lkml.kernel.org/r/20240312153901.3441-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Profiling the munmap() of a zswapped memory region shows 60% of the total
cycles currently going into updating the zswap_pool_total_size.
There are three consumers of this counter:
- store, to enforce the globally configured pool limit
- meminfo & debugfs, to report the size to the user
- shrink, to determine the batch size for each cycle
Instead of aggregating everytime an entry enters or exits the zswap
pool, aggregate the value from the zpools on-demand:
- Stores aggregate the counter anyway upon success. Aggregating to
check the limit instead is the same amount of work.
- Meminfo & debugfs might benefit somewhat from a pre-aggregated
counter, but aren't exactly hotpaths.
- Shrinking can aggregate once for every cycle instead of doing it for
every freed entry. As the shrinker might work on tens or hundreds of
objects per scan cycle, this is a large reduction in aggregations.
The paths that benefit dramatically are swapin, swapoff, and unmaps.
There could be millions of pages being processed until somebody asks for
the pool size again. This eliminates the pool size updates from those
paths entirely.
Top profile entries for a 24G range munmap(), before:
38.54% zswap-unmap [kernel.kallsyms] [k] zs_zpool_total_size
12.51% zswap-unmap [kernel.kallsyms] [k] zpool_get_total_size
9.10% zswap-unmap [kernel.kallsyms] [k] zswap_update_total_size
2.95% zswap-unmap [kernel.kallsyms] [k] obj_cgroup_uncharge_zswap
2.88% zswap-unmap [kernel.kallsyms] [k] __slab_free
2.86% zswap-unmap [kernel.kallsyms] [k] xas_store
and after:
7.70% zswap-unmap [kernel.kallsyms] [k] __slab_free
7.16% zswap-unmap [kernel.kallsyms] [k] obj_cgroup_uncharge_zswap
6.74% zswap-unmap [kernel.kallsyms] [k] xas_store
It was also briefly considered to move to a single atomic in zswap
that is updated by the backends, since zswap only cares about the sum
of all pools anyway. However, zram directly needs per-pool information
out of zsmalloc. To keep the backend from having to update two atomics
every time, I opted for the lazy aggregation instead for now.
Link: https://lkml.kernel.org/r/20240312153901.3441-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
9 out of 16 callers perform a NULL check before calling obj_cgroup_put().
Move the NULL check in the function, similar to mem_cgroup_put(). The
unlikely() NULL check in current_objcg_update() was left alone to avoid
dropping the unlikey() annotation as this a fast path.
Link: https://lkml.kernel.org/r/20240316015803.2777252-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Christian reports a NULL deref in zswap that he bisected down to the zswap
shrinker. The issue also cropped up in the bug trackers of libguestfs [1]
and the Red Hat bugzilla [2].
The problem is that when memcg is disabled with the boot time flag, the
zswap shrinker might get called with sc->memcg == NULL. This is okay in
many places, like the lruvec operations. But it crashes in
memcg_page_state() - which is only used due to the non-node accounting of
cgroup's the zswap memory to begin with.
Nhat spotted that the memcg can be NULL in the memcg-disabled case, and I
was then able to reproduce the crash locally as well.
[1] https://github.com/libguestfs/libguestfs/issues/139
[2] https://bugzilla.redhat.com/show_bug.cgi?id=2275252
Link: https://lkml.kernel.org/r/20240418124043.GC1055428@cmpxchg.org
Link: https://lkml.kernel.org/r/20240417143324.GA1055428@cmpxchg.org
Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Christian Heusel <christian@heusel.eu>
Debugged-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Christian Heusel <christian@heusel.eu>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Richard W.M. Jones <rjones@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: <stable@vger.kernel.org> [v6.8]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Zhongkun He reports data corruption when combining zswap with zram.
The issue is the exclusive loads we're doing in zswap. They assume
that all reads are going into the swapcache, which can assume
authoritative ownership of the data and so the zswap copy can go.
However, zram files are marked SWP_SYNCHRONOUS_IO, and faults will try to
bypass the swapcache. This results in an optimistic read of the swap data
into a page that will be dismissed if the fault fails due to races. In
this case, zswap mustn't drop its authoritative copy.
Link: https://lore.kernel.org/all/CACSyD1N+dUvsu8=zV9P691B9bVq33erwOXNTmEaUbi9DrDeJzw@mail.gmail.com/
Fixes: b9c91c43412f ("mm: zswap: support exclusive loads")
Link: https://lkml.kernel.org/r/20240324210447.956973-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Tested-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Barry Song <baohua@kernel.org>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: <stable@vger.kernel.org> [6.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Kent forwards this bug report of zswap re-entering the block layer
from an IO request allocation and locking up:
[10264.128242] sysrq: Show Blocked State
[10264.128268] task:kworker/20:0H state:D stack:0 pid:143 tgid:143 ppid:2 flags:0x00004000
[10264.128271] Workqueue: bcachefs_io btree_write_submit [bcachefs]
[10264.128295] Call Trace:
[10264.128295] <TASK>
[10264.128297] __schedule+0x3e6/0x1520
[10264.128303] schedule+0x32/0xd0
[10264.128304] schedule_timeout+0x98/0x160
[10264.128308] io_schedule_timeout+0x50/0x80
[10264.128309] wait_for_completion_io_timeout+0x7f/0x180
[10264.128310] submit_bio_wait+0x78/0xb0
[10264.128313] swap_writepage_bdev_sync+0xf6/0x150
[10264.128317] zswap_writeback_entry+0xf2/0x180
[10264.128319] shrink_memcg_cb+0xe7/0x2f0
[10264.128322] __list_lru_walk_one+0xb9/0x1d0
[10264.128325] list_lru_walk_one+0x5d/0x90
[10264.128326] zswap_shrinker_scan+0xc4/0x130
[10264.128327] do_shrink_slab+0x13f/0x360
[10264.128328] shrink_slab+0x28e/0x3c0
[10264.128329] shrink_one+0x123/0x1b0
[10264.128331] shrink_node+0x97e/0xbc0
[10264.128332] do_try_to_free_pages+0xe7/0x5b0
[10264.128333] try_to_free_pages+0xe1/0x200
[10264.128334] __alloc_pages_slowpath.constprop.0+0x343/0xde0
[10264.128337] __alloc_pages+0x32d/0x350
[10264.128338] allocate_slab+0x400/0x460
[10264.128339] ___slab_alloc+0x40d/0xa40
[10264.128345] kmem_cache_alloc+0x2e7/0x330
[10264.128348] mempool_alloc+0x86/0x1b0
[10264.128349] bio_alloc_bioset+0x200/0x4f0
[10264.128352] bio_alloc_clone+0x23/0x60
[10264.128354] alloc_io+0x26/0xf0 [dm_mod 7e9e6b44df4927f93fb3e4b5c782767396f58382]
[10264.128361] dm_submit_bio+0xb8/0x580 [dm_mod 7e9e6b44df4927f93fb3e4b5c782767396f58382]
[10264.128366] __submit_bio+0xb0/0x170
[10264.128367] submit_bio_noacct_nocheck+0x159/0x370
[10264.128368] bch2_submit_wbio_replicas+0x21c/0x3a0 [bcachefs 85f1b9a7a824f272eff794653a06dde1a94439f2]
[10264.128391] btree_write_submit+0x1cf/0x220 [bcachefs 85f1b9a7a824f272eff794653a06dde1a94439f2]
[10264.128406] process_one_work+0x178/0x350
[10264.128408] worker_thread+0x30f/0x450
[10264.128409] kthread+0xe5/0x120
The zswap shrinker resumes the swap_writepage()s that were intercepted
by the zswap store. This will enter the block layer, and may even
enter the filesystem depending on the swap backing file.
Make it respect GFP_NOIO and GFP_NOFS.
Link: https://lore.kernel.org/linux-mm/rc4pk2r42oyvjo4dc62z6sovquyllq56i5cdgcaqbd7wy3hfzr@n4nbxido3fme/
Link: https://lkml.kernel.org/r/20240321182532.60000-1-hannes@cmpxchg.org
Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Kent Overstreet <kent.overstreet@linux.dev>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reported-by: Jérôme Poulin <jeromepoulin@gmail.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Cc: stable@vger.kernel.org [v6.8]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
sg_init_one() relies on linearly mapped low memory for the safe
utilization of virt_to_page(). Otherwise, we trigger a kernel BUG,
kernel BUG at include/linux/scatterlist.h:187!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 2997 Comm: syz-executor198 Not tainted 6.8.0-syzkaller #0
Hardware name: ARM-Versatile Express
PC is at sg_set_buf include/linux/scatterlist.h:187 [inline]
PC is at sg_init_one+0x9c/0xa8 lib/scatterlist.c:143
LR is at sg_init_table+0x2c/0x40 lib/scatterlist.c:128
Backtrace:
[<807e16ac>] (sg_init_one) from [<804c1824>] (zswap_decompress+0xbc/0x208 mm/zswap.c:1089)
r7:83471c80 r6:def6d08c r5:844847d0 r4:ff7e7ef4
[<804c1768>] (zswap_decompress) from [<804c4468>] (zswap_load+0x15c/0x198 mm/zswap.c:1637)
r9:8446eb80 r8:8446eb80 r7:8446eb84 r6:def6d08c r5:00000001 r4:844847d0
[<804c430c>] (zswap_load) from [<804b9644>] (swap_read_folio+0xa8/0x498 mm/page_io.c:518)
r9:844ac800 r8:835e6c00 r7:00000000 r6:df955d4c r5:00000001 r4:def6d08c
[<804b959c>] (swap_read_folio) from [<804bb064>] (swap_cluster_readahead+0x1c4/0x34c mm/swap_state.c:684)
r10:00000000 r9:00000007 r8:df955d4b r7:00000000 r6:00000000 r5:00100cca
r4:00000001
[<804baea0>] (swap_cluster_readahead) from [<804bb3b8>] (swapin_readahead+0x68/0x4a8 mm/swap_state.c:904)
r10:df955eb8 r9:00000000 r8:00100cca r7:84476480 r6:00000001 r5:00000000
r4:00000001
[<804bb350>] (swapin_readahead) from [<8047cde0>] (do_swap_page+0x200/0xcc4 mm/memory.c:4046)
r10:00000040 r9:00000000 r8:844ac800 r7:84476480 r6:00000001 r5:00000000
r4:df955eb8
[<8047cbe0>] (do_swap_page) from [<8047e6c4>] (handle_pte_fault mm/memory.c:5301 [inline])
[<8047cbe0>] (do_swap_page) from [<8047e6c4>] (__handle_mm_fault mm/memory.c:5439 [inline])
[<8047cbe0>] (do_swap_page) from [<8047e6c4>] (handle_mm_fault+0x3d8/0x12b8 mm/memory.c:5604)
r10:00000040 r9:842b3900 r8:7eb0d000 r7:84476480 r6:7eb0d000 r5:835e6c00
r4:00000254
[<8047e2ec>] (handle_mm_fault) from [<80215d28>] (do_page_fault+0x148/0x3a8 arch/arm/mm/fault.c:326)
r10:00000007 r9:842b3900 r8:7eb0d000 r7:00000207 r6:00000254 r5:7eb0d9b4
r4:df955fb0
[<80215be0>] (do_page_fault) from [<80216170>] (do_DataAbort+0x38/0xa8 arch/arm/mm/fault.c:558)
r10:7eb0da7c r9:00000000 r8:80215be0 r7:df955fb0 r6:7eb0d9b4 r5:00000207
r4:8261d0e0
[<80216138>] (do_DataAbort) from [<80200e3c>] (__dabt_usr+0x5c/0x60 arch/arm/kernel/entry-armv.S:427)
Exception stack(0xdf955fb0 to 0xdf955ff8)
5fa0: 00000000 00000000 22d5f800 0008d158
5fc0: 00000000 7eb0d9a4 00000000 00000109 00000000 00000000 7eb0da7c 7eb0da3c
5fe0: 00000000 7eb0d9a0 00000001 00066bd4 00000010 ffffffff
r8:824a9044 r7:835e6c00 r6:ffffffff r5:00000010 r4:00066bd4
Code: 1a000004 e1822003 e8860094 e89da8f0 (e7f001f2)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 1a000004 bne 0x18
4: e1822003 orr r2, r2, r3
8: e8860094 stm r6, {r2, r4, r7}
c: e89da8f0 ldm sp, {r4, r5, r6, r7, fp, sp, pc}
* 10: e7f001f2 udf #18 <-- trapping instruction
Consequently, we have two choices: either employ kmap_to_page() alongside
sg_set_page(), or resort to copying high memory contents to a temporary
buffer residing in low memory. However, considering the introduction of
the WARN_ON_ONCE in commit ef6e06b2ef870 ("highmem: fix kmap_to_page() for
kmap_local_page() addresses"), which specifically addresses high memory
concerns, it appears that memcpy remains the sole viable option.
Link: https://lkml.kernel.org/r/20240318234706.95347-1-21cnbao@gmail.com
Fixes: 270700dd06ca ("mm/zswap: remove the memcpy if acomp is not sleepable")
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reported-by: syzbot+adbc983a1588b7805de3@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/000000000000bbb3d80613f243a6@google.com/
Tested-by: syzbot+adbc983a1588b7805de3@syzkaller.appspotmail.com
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Most compressors are actually CPU-based and won't sleep during compression
and decompression. We should remove the redundant memcpy for them.
This patch checks if the algorithm is sleepable by testing the
CRYPTO_ALG_ASYNC algorithm flag.
Generally speaking, async and sleepable are semantically similar but not
equal. But for compress drivers, they are basically equal at least due to
the below facts.
Firstly, scompress drivers - crypto/deflate.c, lz4.c, zstd.c, lzo.c etc
have no sleep. Secondly, zRAM has been using these scompress drivers for
years in atomic contexts, and never worried those drivers going to sleep.
One exception is that an async driver can sometimes still return
synchronously per Herbert's clarification. In this case, we are still
having a redundant memcpy. But we can't know if one particular acomp
request will sleep or not unless crypto can expose more details for each
specific request from offload drivers.
Link: https://lkml.kernel.org/r/20240222081135.173040-3-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Tested-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Commit bf9b7df23cb3 ("mm/zswap: global lru and shrinker shared by all
zswap_pools") introduced a new lock to protect zswap_next_shrink, instead
of reusing zswap_pools_lock.
But the problem is that it's initialized only when zswap enabled, which
causes bug if zswap_memcg_offline_cleanup() called without zswap enabled.
Fix it by using DEFINE_SPINLOCK() to statically initialize them and define
them as multiple static variables to keep in consistent with the existing
global variables in zswap.
Link: https://lkml.kernel.org/r/20240305075345.1493214-1-chengming.zhou@linux.dev
Fixes: bf9b7df23cb3 ("mm/zswap: global lru and shrinker shared by all zswap_pools")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202403051008.a8cf8a94-lkp@intel.com
Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
All zswap entries will take a reference of zswap_pool when zswap_store(),
and drop it when free. Change it to use the percpu_ref is better for
scalability performance.
Although percpu_ref use a bit more memory which should be ok for our use
case, since we almost have only one zswap_pool to be using. The
performance gain is for zswap_store/load hotpath.
Testing kernel build (32 threads) in tmpfs with memory.max=2GB. (zswap
shrinker and writeback enabled with one 50GB swapfile, on a 128 CPUs
x86-64 machine, below is the average of 5 runs)
mm-unstable zswap-global-lru
real 63.20 63.12
user 1061.75 1062.95
sys 268.74 264.44
[chengming.zhou@linux.dev: fix zswap_pools_lock usages after changing to percpu_ref]
Link: https://lkml.kernel.org/r/20240228154954.3028626-1-chengming.zhou@linux.dev
Link: https://lkml.kernel.org/r/20240210-zswap-global-lru-v3-2-200495333595@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm/zswap: optimize for dynamic zswap_pools", v3.
Dynamic pool creation has been supported for a long time, which maybe not
used so much in practice. But with the per-memcg lru merged, the current
structure of zswap_pool's lru and shrinker become less optimal.
In the current structure, each zswap_pool has its own lru, shrinker and
shrink_work, but only the latest zswap_pool will be the current used.
1. When memory has pressure, all shrinkers of zswap_pools will try to
shrink its lru list, there is no order between them.
2. When zswap limit hit, only the last zswap_pool's shrink_work will
try to shrink its own lru, which is inefficient.
A more natural way is to have a global zswap lru shared between all
zswap_pools, and so is the shrinker. The code becomes much simpler too.
Another optimization is changing zswap_pool kref to percpu_ref, which will
be taken reference by every zswap entry. So the scalability is better.
Testing kernel build (32 threads) in tmpfs with memory.max=2GB. (zswap
shrinker and writeback enabled with one 50GB swapfile, on a 128 CPUs
x86-64 machine, below is the average of 5 runs)
mm-unstable zswap-global-lru
real 63.20 63.12
user 1061.75 1062.95
sys 268.74 264.44
This patch (of 3):
Dynamic zswap_pool creation may create/reuse to have multiple zswap_pools
in a list, only the first will be current used.
Each zswap_pool has its own lru and shrinker, which is not necessary and
has its problem:
1. When memory has pressure, all shrinker of zswap_pools will
try to shrink its own lru, there is no order between them.
2. When zswap limit hit, only the last zswap_pool's shrink_work
will try to shrink its lru list. The rationale here was to
try and empty the old pool first so that we can completely
drop it. However, since we only support exclusive loads now,
the LRU ordering should be entirely decided by the order of
stores, so the oldest entries on the LRU will naturally be
from the oldest pool.
Anyway, having a global lru and shrinker shared by all zswap_pools is
better and efficient.
Link: https://lkml.kernel.org/r/20240210-zswap-global-lru-v3-0-200495333595@bytedance.com
Link: https://lkml.kernel.org/r/20240210-zswap-global-lru-v3-1-200495333595@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
compression returns ENOSPC
We used to rely on the returned -ENOSPC of zpool_malloc() to increase
reject_compress_poor. But the code wouldn't get to there after commit
744e1885922a ("crypto: scomp - fix req->dst buffer overflow") as the new
code will goto out immediately after the special compression case happens.
So there might be no longer a chance to execute zpool_malloc now. We are
incorrectly increasing zswap_reject_compress_fail instead. Thus, we need
to fix the counters handling right after compressions return ENOSPC. This
patch also centralizes the counters handling for all of compress_poor,
compress_fail and alloc_fail.
Link: https://lkml.kernel.org/r/20240219211935.72394-1-21cnbao@gmail.com
Fixes: 744e1885922a ("crypto: scomp - fix req->dst buffer overflow")
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
We may encounter duplicate entry in the zswap_store():
1. swap slot that freed to per-cpu swap cache, doesn't invalidate
the zswap entry, then got reused. This has been fixed.
2. !exclusive load mode, swapin folio will leave its zswap entry
on the tree, then swapout again. This has been removed.
3. one folio can be dirtied again after zswap_store(), so need to
zswap_store() again. This should be handled correctly.
So we must invalidate the old duplicate entry before inserting the
new one, which actually doesn't have to be done at the beginning
of zswap_store().
The good point is that we don't need to lock the tree twice in the normal
store success path. And cleanup the loop as we are here.
Note we still need to invalidate the old duplicate entry when store failed
or zswap is disabled , otherwise the new data in swapfile could be
overwrite by the old data in zswap pool when lru writeback.
Link: https://lkml.kernel.org/r/20240209044112.3883835-1-chengming.zhou@linux.dev
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Since we don't need to leave zswap entry on the zswap tree anymore,
we should remove it from tree once we find it from the tree.
Then after using it, we can directly free it, no concurrent path
can find it from tree. Only the shrinker can see it from lru list,
which will also double check under tree lock, so no race problem.
So we don't need refcount in zswap entry anymore and don't need to
take the spinlock for the second time to invalidate it.
The side effect is that zswap_entry_free() maybe not happen in tree
spinlock, but it's ok since nothing need to be protected by the lock.
Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-6-99d4084260a0@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The !zswap_exclusive_loads_enabled mode will leave compressed copy in
the zswap tree and lru list after the folio swapin.
There are some disadvantages in this mode:
1. It's a waste of memory since there are two copies of data, one is
folio, the other one is compressed data in zswap. And it's unlikely
the compressed data is useful in the near future.
2. If that folio is dirtied, the compressed data must be not useful,
but we don't know and don't invalidate the trashy memory in zswap.
3. It's not reclaimable from zswap shrinker since zswap_writeback_entry()
will always return -EEXIST and terminate the shrinking process.
On the other hand, the only downside of zswap_exclusive_loads_enabled
is a little more cpu usage/latency when compression, and the same if
the folio is removed from swapcache or dirtied.
More explanation by Johannes on why we should consider exclusive load
as the default for zswap:
Caching "swapout work" is helpful when the system is thrashing. Then
recently swapped in pages might get swapped out again very soon. It
certainly makes sense with conventional swap, because keeping a clean
copy on the disk saves IO work and doesn't cost any additional memory.
But with zswap, it's different. It saves some compression work on a
thrashing page. But the act of keeping compressed memory contributes
to a higher rate of thrashing. And that can cause IO in other places
like zswap writeback and file memory.
And the A/B test results of the kernel build in tmpfs with limited memory
can support this theory:
!exclusive exclusive
real 63.80 63.01
user 1063.83 1061.32
sys 290.31 266.15
workingset_refault_anon 2383084.40 1976397.40
workingset_refault_file 44134.00 45689.40
workingset_activate_anon 837878.00 728441.20
workingset_activate_file 4710.00 4085.20
workingset_restore_anon 732622.60 639428.40
workingset_restore_file 1007.00 926.80
workingset_nodereclaim 0.00 0.00
pgscan 14343003.40 12409570.20
pgscan_kswapd 0.00 0.00
pgscan_direct 14343003.40 12409570.20
pgscan_khugepaged 0.00 0.00
Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-5-99d4084260a0@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
cat /sys/kernel/debug/zswap/duplicate_entry
2086447
When testing, the duplicate_entry value is very high, but no warning
message in the kernel log. From the comment of duplicate_entry "Duplicate
store was encountered (rare)", it seems something goes wrong.
Actually it's incremented in the beginning of zswap_store(), which found
its zswap entry has already on the tree. And this is a normal case, since
the folio could leave zswap entry on the tree after swapin, later it's
dirtied and swapout/zswap_store again, found its original zswap entry.
So duplicate_entry should be only incremented in the real bug case, which
already have "WARN_ON(1)", it looks redundant to count bug case, so this
patch just remove it.
Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-4-99d4084260a0@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
When the shrinker encounter an existing folio in swap cache, it means we
are shrinking into the warmer region. We should terminate shrinking if
we're in the dynamic shrinker context.
This patch add LRU_STOP to support this, to avoid overshrinking.
Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-3-99d4084260a0@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
During testing I found there are some times the zswap_writeback_entry()
return -ENOMEM, which is not we expected:
bpftrace -e 'kr:zswap_writeback_entry {@[(int32)retval]=count()}'
@[-12]: 1563
@[0]: 277221
The reason is that __read_swap_cache_async() return NULL because
swapcache_prepare() failed. The reason is that we won't invalidate zswap
entry when swap entry freed to the per-cpu pool, these zswap entries are
still on the zswap tree and lru list.
This patch moves the invalidation ahead to when swap entry freed to the
per-cpu pool, since there is no any benefit to leave trashy zswap entry on
the tree and lru list.
With this patch:
bpftrace -e 'kr:zswap_writeback_entry {@[(int32)retval]=count()}'
@[0]: 259744
Note: large folio can't have zswap entry for now, so don't bother
to add zswap entry invalidation in the large folio swap free path.
Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-2-99d4084260a0@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm/zswap: optimize zswap lru list", v2.
This series is motivated when observe the zswap lru list shrinking, noted
there are some unexpected cases in zswap_writeback_entry().
bpftrace -e 'kr:zswap_writeback_entry {@[(int32)retval]=count()}'
There are some -ENOMEM because when the swap entry is freed to per-cpu
swap pool, it doesn't invalidate/drop zswap entry. Then the shrinker
encounter these trashy zswap entries, it can't be reclaimed and return
-ENOMEM.
So move the invalidation ahead to when swap entry freed to the per-cpu
swap pool, since there is no any benefit to leave trashy zswap entries on
the zswap tree and lru list.
Another case is -EEXIST, which is seen more in the case of
!zswap_exclusive_loads_enabled, in which case the swapin folio will leave
compressed copy on the tree and lru list. And it can't be reclaimed until
the folio is removed from swapcache.
Changing to zswap_exclusive_loads_enabled mode will invalidate when folio
swapin, which has its own drawback if that folio is still clean in
swapcache and swapout again, we need to compress it again. Please see the
commit for details on why we choose exclusive load as the default for
zswap.
Another optimization for -EEXIST is that we add LRU_STOP to support
terminating the shrinking process to avoid evicting warmer region.
Testing using kernel build in tmpfs, one 50GB swapfile and
zswap shrinker_enabled, with memory.max set to 2GB.
mm-unstable zswap-optimize
real 63.90s 63.25s
user 1064.05s 1063.40s
sys 292.32s 270.94s
The main optimization is in sys cpu, about 7% improvement.
This patch (of 6):
Add more comments in shrink_memcg_cb() to describe the deref dance which
is implemented to fix race problem between lru writeback and swapoff, and
the reason why we rotate the entry at the beginning.
Also fix the stale comments in zswap_writeback_entry(), and add more
comments to state that we only deref the tree after we get the swapcache
reference.
Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-0-99d4084260a0@bytedance.com
Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-1-99d4084260a0@bytedance.com
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Suggested-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
shrink_memcg_cb() is called by the shrinker and is based on
zswap_writeback_entry(). Move it in between. Save one fwd decl.
Link: https://lkml.kernel.org/r/20240130014208.565554-21-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Shrinking needs writeback. Naturally, move the writeback code above
the shrinking code. Delete the forward decl.
Link: https://lkml.kernel.org/r/20240130014208.565554-20-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The per-cpu compression init/exit callbacks are awkwardly in the
middle of the shrinker code. Move them up to the compression section.
Link: https://lkml.kernel.org/r/20240130014208.565554-19-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Writeback needs to decompress. Move the (de)compression API above what
will be the consolidated shrinking/writeback code.
Link: https://lkml.kernel.org/r/20240130014208.565554-18-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The higher-level entry operations modify the tree, so move the entry
API after the tree section.
Link: https://lkml.kernel.org/r/20240130014208.565554-17-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
This completes consolidation of the LRU section.
Link: https://lkml.kernel.org/r/20240130014208.565554-16-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The zswap entry section sits awkwardly in the middle of LRU-related
functions. Group the external LRU API functions first.
Link: https://lkml.kernel.org/r/20240130014208.565554-15-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm: zswap: cleanups".
Cleanups and maintenance items that accumulated while reviewing zswap
patches.
This patch (of 20):
The parameters primarily control pool attributes. Move those
operations up to the pool section.
Link: https://lkml.kernel.org/r/20240130014208.565554-1-hannes@cmpxchg.org
Link: https://lkml.kernel.org/r/20240130014208.565554-14-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Move the operations against the global zswap_pools list (current pool,
last, find) to the pool section.
Link: https://lkml.kernel.org/r/20240130014208.565554-13-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Move pool refcounting functions into the pool section. First the
destroy functions, then the get and put which uses them.
__zswap_pool_empty() has an upward reference to the global
zswap_pools, to sanity check it's not the currently active pool that's
being freed. That gets the forward decl for zswap_pool_current().
This puts the get and put function above all callers, so kill the
forward decls as well.
Link: https://lkml.kernel.org/r/20240130014208.565554-12-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The function ordering in zswap.c is a little chaotic, which requires
jumping in unexpected directions when following related code. This is
a series of patches that brings the file into the following order:
- pool functions
- lru functions
- rbtree functions
- zswap entry functions
- compression/backend functions
- writeback & shrinking functions
- store, load, invalidate, swapon, swapoff
- debugfs
- init
But it has to be split up such the moving still produces halfway
readable diffs.
In this patch, move pool allocation and freeing functions.
Link: https://lkml.kernel.org/r/20240130014208.565554-11-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The branching is awkward and duplicates code. The comment about
writeback is also misleading: yes, the entry might have been written
back. Or it might have never been stored in zswap to begin with due to
a rejection - zswap_invalidate() is called on all exiting swap entries.
Link: https://lkml.kernel.org/r/20240130014208.565554-10-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
- Remove dupentry, reusing entry works just fine.
- Rename pool to shrink_pool, as this one actually is confusing.
- Remove page, use folio_nid() and kmap_local_folio() directly.
- Set entry->swpentry in a common path.
- Move value and src to local scope of use.
Link: https://lkml.kernel.org/r/20240130014208.565554-9-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
zswap_store() is long and mixes work at the zswap layer with work at
the backend and compression layer. Move compression & backend work to
zswap_compress(), mirroring zswap_decompress().
Link: https://lkml.kernel.org/r/20240130014208.565554-8-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Link: https://lkml.kernel.org/r/20240130014208.565554-7-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Remove stale comment and unnecessary local variable.
Link: https://lkml.kernel.org/r/20240130014208.565554-6-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Put a standard sanity check on zswap_entry_get() for UAF scenario.
Link: https://lkml.kernel.org/r/20240130014208.565554-5-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Move it up to the other tree and refcounting functions.
Link: https://lkml.kernel.org/r/20240130014208.565554-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
There is only one caller and the function is trivial. Inline it.
Link: https://lkml.kernel.org/r/20240130014208.565554-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
There is a zswap_entry_ namespace with multiple functions already.
Link: https://lkml.kernel.org/r/20240130014208.565554-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Since the only user zswap_lru_putback() has gone, remove
list_lru_putback() too.
Link: https://lkml.kernel.org/r/20240126-zswap-writeback-race-v2-3-b10479847099@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chris Li <chriscli@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
LRU writeback has race problem with swapoff, as spotted by Yosry [1]:
CPU1 CPU2
shrink_memcg_cb swap_off
list_lru_isolate zswap_invalidate
zswap_swapoff
kfree(tree)
// UAF
spin_lock(&tree->lock)
The problem is that the entry in lru list can't protect the tree from
being swapoff and freed, and the entry also can be invalidated and freed
concurrently after we unlock the lru lock.
We can fix it by moving the swap cache allocation ahead before referencing
the tree, then check invalidate race with tree lock, only after that we
can safely deref the entry. Note we couldn't deref entry or tree anymore
after we unlock the folio, since we depend on this to hold on swapoff.
So this patch moves all tree and entry usage to zswap_writeback_entry(),
we only use the copied swpentry on the stack to allocate swap cache and if
returned with folio locked we can reference the tree safely. Then we can
check invalidate race with tree lock, the following things is much the
same like zswap_load().
Since we can't deref the entry after zswap_writeback_entry(), we can't use
zswap_lru_putback() anymore, instead we rotate the entry in the beginning.
And it will be unlinked and freed when invalidated if writeback success.
Another change is we don't update the memcg nr_zswap_protected in the
-ENOMEM and -EEXIST cases anymore. -EEXIST case means we raced with
swapin or concurrent shrinker action, since swapin already have memcg
nr_zswap_protected updated, don't need double counts here. For concurrent
shrinker, the folio will be writeback and freed anyway. -ENOMEM case is
extremely rare and doesn't happen spuriously either, so don't bother
distinguishing this case.
[1] https://lore.kernel.org/all/CAJD7tkasHsRnT_75-TXsEe58V9_OW6m3g6CF7Kmsvz8CKRG_EA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20240126-zswap-writeback-race-v2-2-b10479847099@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chris Li <chriscli@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Commit 7310895779624 ("mm: zswap: tighten up entry invalidation") removed
the usage of tree argument, delete it.
Link: https://lkml.kernel.org/r/20240125081423.1200336-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
During swapoff, try_to_unuse() makes sure that zswap_invalidate() is
called for all swap entries before zswap_swapoff() is called. This means
that all zswap entries should already be removed from the tree. Simplify
zswap_swapoff() by removing the trees cleanup code, and leave an assertion
in its place.
Link: https://lkml.kernel.org/r/20240124045113.415378-3-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Each swapfile has one rb-tree to search the mapping of swp_entry_t to
zswap_entry, that use a spinlock to protect, which can cause heavy lock
contention if multiple tasks zswap_store/load concurrently.
Optimize the scalability problem by splitting the zswap rb-tree into
multiple rb-trees, each corresponds to SWAP_ADDRESS_SPACE_PAGES (64M),
just like we did in the swap cache address_space splitting.
Although this method can't solve the spinlock contention completely, it
can mitigate much of that contention. Below is the results of kernel
build in tmpfs with zswap shrinker enabled:
linux-next zswap-lock-optimize
real 1m9.181s 1m3.820s
user 17m44.036s 17m40.100s
sys 7m37.297s 4m54.622s
So there are clearly improvements.
Link: https://lkml.kernel.org/r/20240117-b4-zswap-lock-optimize-v2-2-b5cc55479090@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chris Li <chriscli@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm/zswap: optimize the scalability of zswap rb-tree", v2.
When testing the zswap performance by using kernel build -j32 in a tmpfs
directory, I found the scalability of zswap rb-tree is not good, which is
protected by the only spinlock. That would cause heavy lock contention if
multiple tasks zswap_store/load concurrently.
So a simple solution is to split the only one zswap rb-tree into multiple
rb-trees, each corresponds to SWAP_ADDRESS_SPACE_PAGES (64M). This idea
is from the commit 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB
trunks").
Although this method can't solve the spinlock contention completely, it
can mitigate much of that contention. Below is the results of kernel
build in tmpfs with zswap shrinker enabled:
linux-next zswap-lock-optimize
real 1m9.181s 1m3.820s
user 17m44.036s 17m40.100s
sys 7m37.297s 4m54.622s
So there are clearly improvements. And it's complementary with the
ongoing zswap xarray conversion by Chris. Anyway, I think we can also
merge this first, it's complementary IMHO. So I just refresh and resend
this for further discussion.
This patch (of 2):
Not all zswap interfaces can handle the absence of the zswap rb-tree,
actually only zswap_store() has handled it for now.
To make things simple, we make sure each swapfile always have the zswap
rb-tree prepared before being enabled and used. The preparation is
unlikely to fail in practice, this patch just make it explicit.
Link: https://lkml.kernel.org/r/20240117-b4-zswap-lock-optimize-v2-0-b5cc55479090@bytedance.com
Link: https://lkml.kernel.org/r/20240117-b4-zswap-lock-optimize-v2-1-b5cc55479090@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chris Li <chriscli@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The core-api create_workqueue is deprecated, this patch replaces the
create_workqueue with alloc_workqueue. The previous implementation
workqueue of zswap was a bounded workqueue, this patch uses
alloc_workqueue() to create an unbounded workqueue. The WQ_UNBOUND
attribute is desirable making the workqueue not localized to a specific
cpu so that the scheduler is free to exercise improvisations in any
demanding scenarios for offloading cpu time slices for workqueues. For
example if any other workqueues of the same primary cpu had to be served
which are WQ_HIGHPRI and WQ_CPU_INTENSIVE. Also Unbound workqueue happens
to be more efficient in a system during memory pressure scenarios in
comparison to a bounded workqueue.
shrink_wq = alloc_workqueue("zswap-shrink",
WQ_UNBOUND|WQ_MEM_RECLAIM, 1);
Overall the change suggested in this patch should be seamless and does not
alter the existing behavior, other than the improvisation to be an
unbounded workqueue.
Link: https://lkml.kernel.org/r/20240116133145.12454-1-debug.penguin32@gmail.com
Signed-off-by: Ronald Monthero <debug.penguin32@gmail.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
We have to invalidate any duplicate entry even when !zswap_enabled since
zswap can be disabled anytime. If the folio store success before, then
got dirtied again but zswap disabled, we won't invalidate the old
duplicate entry in the zswap_store(). So later lru writeback may
overwrite the new data in swapfile.
Link: https://lkml.kernel.org/r/20240208023254.3873823-1-chengming.zhou@linux.dev
Fixes: 42c06a0e8ebe ("mm: kill frontswap")
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
When a folio is swapped in, the protection size of the corresponding zswap
LRU is incremented, so that the zswap shrinker is more conservative with
its reclaiming action. This field is embedded within the struct lruvec,
so updating it requires looking up the folio's memcg and lruvec. However,
currently this lookup can happen after the folio is unlocked, for instance
if a new folio is allocated, and swap_read_folio() unlocks the folio
before returning. In this scenario, there is no stability guarantee for
the binding between a folio and its memcg and lruvec:
* A folio's memcg and lruvec can be freed between the lookup and the
update, leading to a UAF.
* Folio migration can clear the now-unlocked folio's memcg_data, which
directs the zswap LRU protection size update towards the root memcg
instead of the original memcg. This was recently picked up by the
syzbot thanks to a warning in the inlined folio_lruvec() call.
Move the zswap LRU protection range update above the swap_read_folio()
call, and only when a new page is allocated, to prevent this.
[nphamcs@gmail.com: add VM_WARN_ON_ONCE() to zswap_folio_swapin()]
Link: https://lkml.kernel.org/r/20240206180855.3987204-1-nphamcs@gmail.com
[nphamcs@gmail.com: remove unneeded if (folio) checks]
Link: https://lkml.kernel.org/r/20240206191355.83755-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20240205232442.3240571-1-nphamcs@gmail.com
Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure")
Reported-by: syzbot+17a611d10af7d18a7092@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/000000000000ae47f90610803260@google.com/
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In zswap_writeback_entry(), after we get a folio from
__read_swap_cache_async(), we grab the tree lock again to check that the
swap entry was not invalidated and recycled. If it was, we delete the
folio we just added to the swap cache and exit.
However, __read_swap_cache_async() returns the folio locked when it is
newly allocated, which is always true for this path, and the folio is
ref'd. Make sure to unlock and put the folio before returning.
This was discovered by code inspection, probably because this path handles
a race condition that should not happen often, and the bug would not crash
the system, it will only strand the folio indefinitely.
Link: https://lkml.kernel.org/r/20240125085127.1327013-1-yosryahmed@google.com
Fixes: 04fc7816089c ("mm: fix zswap writeback race condition")
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
LRU_SKIP can only be returned if we don't ever dropped lru lock, or we
need to return LRU_RETRY to restart from the head of lru list.
Otherwise, the iteration might continue from a cursor position that was
freed while the locks were dropped.
Actually we may need to introduce another LRU_STOP to really terminate the
ongoing shrinking scan process, when we encounter a warm page already in
the swap cache. The current list_lru implementation doesn't have this
function to early break from __list_lru_walk_one.
Link: https://lkml.kernel.org/r/20240126-zswap-writeback-race-v2-1-b10479847099@bytedance.com
Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure")
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Chris Li <chriscli@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
In the per-memcg LRU universe, LRU removal uses entry->objcg to determine
which list count needs to be decreased. Drop the objcg reference after
updating the LRU, to fix a possible use-after-free.
Link: https://lkml.kernel.org/r/20240130013438.565167-1-hannes@cmpxchg.org
Fixes: a65b0e7607cc ("zswap: make shrinking memcg-aware")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
During our experiment with zswap, we sometimes observe swap IOs due to
occasional zswap store failures and writebacks-to-swap. These swapping
IOs prevent many users who cannot tolerate swapping from adopting zswap to
save memory and improve performance where possible.
This patch adds the option to disable this behavior entirely: do not
writeback to backing swapping device when a zswap store attempt fail, and
do not write pages in the zswap pool back to the backing swap device (both
when the pool is full, and when the new zswap shrinker is called).
This new behavior can be opted-in/out on a per-cgroup basis via a new
cgroup file. By default, writebacks to swap device is enabled, which is
the previous behavior. Initially, writeback is enabled for the root
cgroup, and a newly created cgroup will inherit the current setting of its
parent.
Note that this is subtly different from setting memory.swap.max to 0, as
it still allows for pages to be stored in the zswap pool (which itself
consumes swap space in its current form).
This patch should be applied on top of the zswap shrinker series:
https://lore.kernel.org/linux-mm/20231130194023.4102148-1-nphamcs@gmail.com/
as it also disables the zswap shrinker, a major source of zswap
writebacks.
For the most part, this feature is motivated by internal parties who
have already established their opinions regarding swapping - the
workloads that are highly sensitive to IO, and especially those who are
using servers with really slow disk performance (for instance, massive
but slow HDDs). For these folks, it's impossible to convince them to
even entertain zswap if swapping also comes as a packaged deal.
Writeback disabling is quite a useful feature in these situations - on
a mixed workloads deployment, they can disable writeback for the more
IO-sensitive workloads, and enable writeback for other background
workloads.
For instance, on a server with HDD, I allocate memories and populate
them with random values (so that zswap store will always fail), and
specify memory.high low enough to trigger reclaim. The time it takes
to allocate the memories and just read through it a couple of times
(doing silly things like computing the values' average etc.):
zswap.writeback disabled:
real 0m30.537s
user 0m23.687s
sys 0m6.637s
0 pages swapped in
0 pages swapped out
zswap.writeback enabled:
real 0m45.061s
user 0m24.310s
sys 0m8.892s
712686 pages swapped in
461093 pages swapped out
(the last two lines are from vmstat -s).
[nphamcs@gmail.com: add a comment about recurring zswap store failures leading to reclaim inefficiency]
Link: https://lkml.kernel.org/r/20231221005725.3446672-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20231207192406.3809579-1-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: David Heidelberg <david@ixit.cz>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Both callers now have a folio, so pass that in instead of the page.
Removes a few hidden calls to compound_head().
Link: https://lkml.kernel.org/r/20231213215842.671461-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "More swap folio conversions".
These all seem like fairly straightforward conversions to me. A lot of
compound_head() calls get removed. And page_swap_info(), which is nice.
This patch (of 13):
Move the folio->page conversion into the callers that actually want that.
Most of the callers are happier with the folio anyway. If the
page_allocated boolean is set, the folio allocated is of order-0, so it is
safe to pass the page directly to swap_readpage().
Link: https://lkml.kernel.org/r/20231213215842.671461-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20231213215842.671461-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
First of all, we need to rename acomp_ctx->dstmem field to buffer, since
we are now using for purposes other than compression.
Then we change per-cpu mutex and buffer to per-acomp_ctx, since them
belong to the acomp_ctx and are necessary parts when used in the
compress/decompress contexts.
So we can remove the old per-cpu mutex and dstmem.
Link: https://lkml.kernel.org/r/20231213-zswap-dstmem-v5-5-9382162bbf05@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Chris Li <chrisl@kernel.org> (Google)
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Also after the common decompress part goes to __zswap_load(), we can
cleanup the zswap_writeback_entry() a little.
Link: https://lkml.kernel.org/r/20231213-zswap-dstmem-v5-4-9382162bbf05@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Chris Li <chrisl@kernel.org> (Google)
Cc: Barry Song <21cnbao@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
After the common decompress part goes to __zswap_load(), we can cleanup
the zswap_load() a little.
Link: https://lkml.kernel.org/r/20231213-zswap-dstmem-v5-3-9382162bbf05@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Chis Li <chrisl@kernel.org> (Google)
Cc: Barry Song <21cnbao@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
zswap_load() and zswap_writeback_entry() have the same part that
decompress the data from zswap_entry to page, so refactor out the common
part as __zswap_load(entry, page).
Link: https://lkml.kernel.org/r/20231213-zswap-dstmem-v5-2-9382162bbf05@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Chris Li <chrisl@kernel.org> (Google)
Cc: Barry Song <21cnbao@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm/zswap: dstmem reuse optimizations and cleanups", v5.
The problem this series tries to optimize is that zswap_load() and
zswap_writeback_entry() have to malloc a temporary memory to support
!zpool_can_sleep_mapped(). We can avoid it by reusing the percpu
crypto_acomp_ctx->dstmem, which is also used by zswap_store() and
protected by the same percpu crypto_acomp_ctx->mutex.
This patch (of 5):
In the !zpool_can_sleep_mapped() case such as zsmalloc, we need to first
copy the entry->handle memory to a temporary memory, which is allocated
using kmalloc.
Obviously we can reuse the per-compressor dstmem to avoid allocating every
time, since it's percpu-compressor and protected in percpu mutex.
Link: https://lkml.kernel.org/r/20231213-zswap-dstmem-v5-0-9382162bbf05@bytedance.com
Link: https://lkml.kernel.org/r/20231213-zswap-dstmem-v5-1-9382162bbf05@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Chris Li <chrisl@kernel.org> (Google)
Cc: Barry Song <21cnbao@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Stats flushing for memcg currently follows the following rules:
- Always flush the entire memcg hierarchy (i.e. flush the root).
- Only one flusher is allowed at a time. If someone else tries to flush
concurrently, they skip and return immediately.
- A periodic flusher flushes all the stats every 2 seconds.
The reason this approach is followed is because all flushes are serialized
by a global rstat spinlock. On the memcg side, flushing is invoked from
userspace reads as well as in-kernel flushers (e.g. reclaim, refault,
etc). This approach aims to avoid serializing all flushers on the global
lock, which can cause a significant performance hit under high
concurrency.
This approach has the following problems:
- Occasionally a userspace read of the stats of a non-root cgroup will
be too expensive as it has to flush the entire hierarchy [1].
- Sometimes the stats accuracy are compromised if there is an ongoing
flush, and we skip and return before the subtree of interest is
actually flushed, yielding stale stats (by up to 2s due to periodic
flushing). This is more visible when reading stats from userspace,
but can also affect in-kernel flushers.
The latter problem is particulary a concern when userspace reads stats
after an event occurs, but gets stats from before the event. Examples:
- When memory usage / pressure spikes, a userspace OOM handler may look
at the stats of different memcgs to select a victim based on various
heuristics (e.g. how much private memory will be freed by killing
this). Reading stale stats from before the usage spike in this case
may cause a wrongful OOM kill.
- A proactive reclaimer may read the stats after writing to
memory.reclaim to measure the success of the reclaim operation. Stale
stats from before reclaim may give a false negative.
- Reading the stats of a parent and a child memcg may be inconsistent
(child larger than parent), if the flush doesn't happen when the
parent is read, but happens when the child is read.
As for in-kernel flushers, they will occasionally get stale stats. No
regressions are currently known from this, but if there are regressions,
they would be very difficult to debug and link to the source of the
problem.
This patch aims to fix these problems by restoring subtree flushing, and
removing the unified/coalesced flushing logic that skips flushing if there
is an ongoing flush. This change would introduce a significant regression
with global stats flushing thresholds. With per-memcg stats flushing
thresholds, this seems to perform really well. The thresholds protect the
underlying lock from unnecessary contention.
This patch was tested in two ways to ensure the latency of flushing is
up to par, on a machine with 384 cpus:
- A synthetic test with 5000 concurrent workers in 500 cgroups doing
allocations and reclaim, as well as 1000 readers for memory.stat
(variation of [2]). No regressions were noticed in the total runtime.
Note that significant regressions in this test are observed with
global stats thresholds, but not with per-memcg thresholds.
- A synthetic stress test for concurrently reading memcg stats while
memory allocation/freeing workers are running in the background,
provided by Wei Xu [3]. With 250k threads reading the stats every
100ms in 50k cgroups, 99.9% of reads take <= 50us. Less than 0.01%
of reads take more than 1ms, and no reads take more than 100ms.
[1] https://lore.kernel.org/lkml/CABWYdi0c6__rh-K7dcM_pkf9BJdTRtAU08M43KO9ME4-dsgfoQ@mail.gmail.com/
[2] https://lore.kernel.org/lkml/CAJD7tka13M-zVZTyQJYL1iUAYvuQ1fcHbCjcOBZcz6POYTV-4g@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CAAPL-u9D2b=iF5Lf_cRnKxUfkiEe0AMDTu6yhrUAzX0b6a6rDg@mail.gmail.com/
[akpm@linux-foundation.org: fix mm/zswap.c]
[yosryahmed@google.com: remove stats flushing mutex]
Link: https://lkml.kernel.org/r/CAJD7tkZgP3m-VVPn+fF_YuvXeQYK=tZZjJHj=dzD=CcSSpp2qg@mail.gmail.com
Link: https://lkml.kernel.org/r/20231129032154.3710765-6-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Tested-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ivan Babrou <ivan@cloudflare.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Wei Xu <weixugc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently, we only shrink the zswap pool when the user-defined limit is
hit. This means that if we set the limit too high, cold data that are
unlikely to be used again will reside in the pool, wasting precious
memory. It is hard to predict how much zswap space will be needed ahead
of time, as this depends on the workload (specifically, on factors such as
memory access patterns and compressibility of the memory pages).
This patch implements a memcg- and NUMA-aware shrinker for zswap, that is
initiated when there is memory pressure. The shrinker does not have any
parameter that must be tuned by the user, and can be opted in or out on a
per-memcg basis.
Furthermore, to make it more robust for many workloads and prevent
overshrinking (i.e evicting warm pages that might be refaulted into
memory), we build in the following heuristics:
* Estimate the number of warm pages residing in zswap, and attempt to
protect this region of the zswap LRU.
* Scale the number of freeable objects by an estimate of the memory
saving factor. The better zswap compresses the data, the fewer pages
we will evict to swap (as we will otherwise incur IO for relatively
small memory saving).
* During reclaim, if the shrinker encounters a page that is also being
brought into memory, the shrinker will cautiously terminate its
shrinking action, as this is a sign that it is touching the warmer
region of the zswap LRU.
As a proof of concept, we ran the following synthetic benchmark: build the
linux kernel in a memory-limited cgroup, and allocate some cold data in
tmpfs to see if the shrinker could write them out and improved the overall
performance. Depending on the amount of cold data generated, we observe
from 14% to 35% reduction in kernel CPU time used in the kernel builds.
[nphamcs@gmail.com: check shrinker enablement early, use less costly stat flushing]
Link: https://lkml.kernel.org/r/20231206194456.3234203-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20231130194023.4102148-7-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Since zswap now writes back pages from memcg-specific LRUs, we now need a
new stat to show writebacks count for each memcg.
[nphamcs@gmail.com: rename ZSWP_WB to ZSWPWB]
Link: https://lkml.kernel.org/r/20231205193307.2432803-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20231130194023.4102148-5-nphamcs@gmail.com
Suggested-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently, we only have a single global LRU for zswap. This makes it
impossible to perform worload-specific shrinking - an memcg cannot
determine which pages in the pool it owns, and often ends up writing pages
from other memcgs. This issue has been previously observed in practice
and mitigated by simply disabling memcg-initiated shrinking:
https://lore.kernel.org/all/20230530232435.3097106-1-nphamcs@gmail.com/T/#u
This patch fully resolves the issue by replacing the global zswap LRU
with memcg- and NUMA-specific LRUs, and modify the reclaim logic:
a) When a store attempt hits an memcg limit, it now triggers a
synchronous reclaim attempt that, if successful, allows the new
hotter page to be accepted by zswap.
b) If the store attempt instead hits the global zswap limit, it will
trigger an asynchronous reclaim attempt, in which an memcg is
selected for reclaim in a round-robin-like fashion.
[nphamcs@gmail.com: use correct function for the onlineness check, use mem_cgroup_iter_break()]
Link: https://lkml.kernel.org/r/20231205195419.2563217-1-nphamcs@gmail.com
[nphamcs@gmail.com: drop the pool's reference at the end of the writeback step]
Link: https://lkml.kernel.org/r/20231206030627.4155634-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20231130194023.4102148-4-nphamcs@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Co-developed-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
kmap_atomic() has been deprecated in favor of kmap_local_page().
Therefore, replace kmap_atomic() with kmap_local_page() in
zswap.c.
kmap_atomic() is implemented like a kmap_local_page() which also disables
page-faults and preemption (the latter only in !PREEMPT_RT kernels). The
kernel virtual addresses returned by these two API are only valid in the
context of the callers (i.e., they cannot be handed to other threads).
With kmap_local_page() the mappings are per thread and CPU local like in
kmap_atomic(); however, they can handle page-faults and can be called from
any context (including interrupts). The tasks that call kmap_local_page()
can be preempted and, when they are scheduled to run again, the kernel
virtual addresses are restored and are still valid.
In mm/zswap.c, the blocks of code between the mappings and un-mappings do
not depend on the above-mentioned side effects of kmap_atomic(), so that
the mere replacements of the old API with the new one is all that is
required (i.e., there is no need to explicitly call pagefault_disable()
and/or preempt_disable()).
Link: https://lkml.kernel.org/r/20231127160058.586446-1-fabio.maria.de.francesco@linux.intel.com
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Chris Li <chrisl@kernel.org> (Google)
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
During a zswap store attempt, the compression algorithm could fail (for
e.g due to the page containing incompressible random data). This is not
tracked in any of existing zswap counters, making it hard to monitor for
and investigate. We have run into this problem several times in our
internal investigations on zswap store failures.
This patch adds a dedicated debugfs counter for compression algorithm
failures.
Link: https://lkml.kernel.org/r/20231024234509.2680539-1-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Shrink shmem's stack usage by eliminating the pseudo-vma from its folio
allocation. alloc_pages_mpol(gfp, order, pol, ilx, nid) becomes the
principal actor for passing mempolicy choice down to __alloc_pages(),
rather than vma_alloc_folio(gfp, order, vma, addr, hugepage).
vma_alloc_folio() and alloc_pages() remain, but as wrappers around
alloc_pages_mpol(). alloc_pages_bulk_*() untouched, except to provide the
additional args to policy_nodemask(), which subsumes policy_node().
Cleanup throughout, cutting out some unhelpful "helpers".
It would all be much simpler without MPOL_INTERLEAVE, but that adds a
dynamic to the constant mpol: complicated by v3.6 commit 09c231cb8bfd
("tmpfs: distribute interleave better across nodes"), which added ino bias
to the interleave, hidden from mm/mempolicy.c until this commit.
Hence "ilx" throughout, the "interleave index". Originally I thought it
could be done just with nid, but that's wrong: the nodemask may come from
the shared policy layer below a shmem vma, or it may come from the task
layer above a shmem vma; and without the final nodemask then nodeid cannot
be decided. And how ilx is applied depends also on page order.
The interleave index is almost always irrelevant unless MPOL_INTERLEAVE:
with one exception in alloc_pages_mpol(), where the NO_INTERLEAVE_INDEX
passed down from vma-less alloc_pages() is also used as hint not to use
THP-style hugepage allocation - to avoid the overhead of a hugepage arg
(though I don't understand why we never just added a GFP bit for THP - if
it actually needs a different allocation strategy from other pages of the
same order). vma_alloc_folio() still carries its hugepage arg here, but
it is not used, and should be removed when agreed.
get_vma_policy() no longer allows a NULL vma: over time I believe we've
eradicated all the places which used to need it e.g. swapoff and madvise
used to pass NULL vma to read_swap_cache_async(), but now know the vma.
[hughd@google.com: handle NULL mpol being passed to __read_swap_cache_async()]
Link: https://lkml.kernel.org/r/ea419956-4751-0102-21f7-9c93cb957892@google.com
Link: https://lkml.kernel.org/r/74e34633-6060-f5e3-aee-7040d43f2e93@google.com
Link: https://lkml.kernel.org/r/1738368e-bac0-fd11-ed7f-b87142a939fe@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun heo <tj@kernel.org>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Domenico Cerasuolo <mimmocerasuolo@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
When a zswap store fails due to the limit, it acquires a pool reference
and queues the shrinker. When the shrinker runs, it drops the reference.
However, there can be multiple store attempts before the shrinker wakes up
and runs once. This results in reference leaks and eventual saturation
warnings for the pool refcount.
Fix this by dropping the reference again when the shrinker is already
queued. This ensures one reference per shrinker run.
Link: https://lkml.kernel.org/r/20231006160024.170748-1-hannes@cmpxchg.org
Fixes: 45190f01dd40 ("mm/zswap.c: add allocation hysteresis if pool limit is hit")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Chris Mason <clm@fb.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: <stable@vger.kernel.org> [5.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
While stress-testing zswap a memory corruption was happening when writing
back pages. __frontswap_store used to check for duplicate entries before
attempting to store a page in zswap, this was because if the store fails
the old entry isn't removed from the tree. This change removes duplicate
entries in zswap_store before the actual attempt.
[cerasuolodomenico@gmail.com: add a warning and a comment, per Johannes]
Link: https://lkml.kernel.org/r/20230925130002.1929369-1-cerasuolodomenico@gmail.com
Link: https://lkml.kernel.org/r/20230922172211.1704917-1-cerasuolodomenico@gmail.com
Fixes: 42c06a0e8ebe ("mm: kill frontswap")
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Let's simply work on the folio directly and remove the helpers.
Link: https://lkml.kernel.org/r/20230821160849.531668-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Chris Li <chrisl@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Since commit 0bb488498c98 ("mm: zswap: remove zswap_header"), the 'offset'
has been replaced by swpentry, update the comment for it, and also add
comment for 'objcg'.
Link: https://lkml.kernel.org/r/20230808062056.292950-1-xiujianfeng@huaweicloud.com
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The __read_swap_cache_async() interface isn't more difficult to understand
than what the helper abstracts. Save the indirection and a level of
indentation for the primary work of the writeback func.
Link: https://lkml.kernel.org/r/20230727162343.1415598-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Removing a zswap entry from the tree is tied to an explicit operation
that's supposed to drop the base reference: swap invalidation, exclusive
load, duplicate store. Don't silently remove the entry on final put, but
instead warn if an entry is in tree without reference.
While in that diff context, convert a BUG_ON to a WARN_ON_ONCE. No need
to crash on a refcount underflow.
Link: https://lkml.kernel.org/r/20230727162343.1415598-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm: zswap: three cleanups".
Three small cleanups to zswap, the first one suggested by Yosry during the
frontswap removal.
This patch (of 3):
Minor cleanup. Instead of open-coding the tree deletion and the put, use
the zswap_invalidate_entry() convenience helper.
Link: https://lkml.kernel.org/r/20230727162343.1415598-1-hannes@cmpxchg.org
Link: https://lkml.kernel.org/r/20230727162343.1415598-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Only convert a few easy parts of this function to use the folio passed in;
convert back to struct page for the majority of it. Removes three hidden
calls to compound_head().
Link: https://lkml.kernel.org/r/20230715042343.434588-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
As the one caller now has a folio, pass it in and use it. Removes three
calls to compound_head().
Link: https://lkml.kernel.org/r/20230715042343.434588-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "Followup folio conversions for zswap".
With frontswap killed, it's worth converting the zswap_load() and
zswap_store() functions to take a folio instead of a page pointer. They
aren't converted to support large folios, but there are a lot of
unnecessary calls to compound_head() that are removed by these patches.
This patch (of 4):
Only convert a few easy parts of this function to use the folio passed in;
convert back to struct page for the majority of it. This does remove a
few hidden calls to compound_head().
Link: https://lkml.kernel.org/r/20230715042343.434588-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20230715042343.434588-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The only user of frontswap is zswap, and has been for a long time. Have
swap call into zswap directly and remove the indirection.
[hannes@cmpxchg.org: remove obsolete comment, per Yosry]
Link: https://lkml.kernel.org/r/20230719142832.GA932528@cmpxchg.org
[fengwei.yin@intel.com: don't warn if none swapcache folio is passed to zswap_load]
Link: https://lkml.kernel.org/r/20230810095652.3905184-1-fengwei.yin@intel.com
Link: https://lkml.kernel.org/r/20230717160227.GA867137@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Support using multiple zpools of the same type in zswap, for concurrency
purposes. A fixed number of 32 zpools is suggested by this commit, which
was determined empirically. It can be later changed or made into a config
option if needed.
On a setup with zswap and zsmalloc, comparing a single zpool to 32 zpools
shows improvements in the zsmalloc lock contention, especially on the swap
out path.
The following shows the perf analysis of the swapout path when 10
workloads are simultaneously reclaiming and refaulting tmpfs pages. There
are some improvements on the swap in path as well, but less significant.
1 zpool:
|--28.99%--zswap_frontswap_store
|
<snip>
|
|--8.98%--zpool_map_handle
| |
| --8.98%--zs_zpool_map
| |
| --8.95%--zs_map_object
| |
| --8.38%--_raw_spin_lock
| |
| --7.39%--queued_spin_lock_slowpath
|
|--8.82%--zpool_malloc
| |
| --8.82%--zs_zpool_malloc
| |
| --8.80%--zs_malloc
| |
| |--7.21%--_raw_spin_lock
| | |
| | --6.81%--queued_spin_lock_slowpath
<snip>
32 zpools:
|--16.73%--zswap_frontswap_store
|
<snip>
|
|--1.81%--zpool_malloc
| |
| --1.81%--zs_zpool_malloc
| |
| --1.79%--zs_malloc
| |
| --0.73%--obj_malloc
|
|--1.06%--zswap_update_total_size
|
|--0.59%--zpool_map_handle
| |
| --0.59%--zs_zpool_map
| |
| --0.57%--zs_map_object
| |
| --0.51%--_raw_spin_lock
<snip>
Link: https://lkml.kernel.org/r/20230620194644.3142384-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Yu Zhao <yuzhao@google.com>
Acked-by: Chris Li (Google) <chrisl@kernel.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Nhat Pham <nphamcs@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
If exclusive loads are enabled for zswap, we invalidate the entry before
returning from zswap_frontswap_load(), after dropping the local reference.
However, the tree lock is dropped during decompression after the local
reference is acquired, so the entry could be invalidated before we drop
the local ref. If this happens, the entry is freed once we drop the local
ref, and zswap_invalidate_entry() tries to invalidate an already freed
entry.
Fix this by:
(a) Making sure zswap_invalidate_entry() is always called with a local
ref held, to avoid being called on a freed entry.
(b) Making sure zswap_invalidate_entry() only drops the ref if the entry
was actually on the rbtree. Otherwise, another invalidation could
have already happened, and the initial ref is already dropped.
With these changes, there is no need to check that there is no need to
make sure the entry still exists in the tree in zswap_reclaim_entry()
before invalidating it, as zswap_reclaim_entry() will make this check
internally.
Link: https://lkml.kernel.org/r/20230621093009.637544-1-yosryahmed@google.com
Fixes: b9c91c43412f ("mm: zswap: support exclusive loads")
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
|
|
When an entry started writeback, it used to be invalidated with ref count
logic alone, meaning that it would stay on the tree until all references
were put. The problem with this behavior is that as soon as the writeback
started, the ownership of the data held by the entry is passed to the
swapcache and should not be left in zswap too. Currently there are no
known issues because of this, but this change explicitly invalidates an
entry that started writeback to reduce opportunities for future bugs.
This patch is a follow up on the series titled "mm: zswap: move writeback
LRU from zpool to zswap" + commit f090b7949768("mm: zswap: support
exclusive loads").
Link: https://lkml.kernel.org/r/20230614143122.74471-1-cerasuolodomenico@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Previously, zswap_header served the purpose of storing the swpentry within
zpool pages. This allowed zpool implementations to pass relevant
information to the writeback function. However, with the current
implementation, writeback is directly handled within zswap. Consequently,
there is no longer a necessity for zswap_header, as the swp_entry_t can be
stored directly in zswap_entry.
Link: https://lkml.kernel.org/r/20230612093815.133504-8-cerasuolodomenico@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Tested-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
zswap_writeback_entry() used to be a callback for the backends, which
don't know about struct zswap_entry.
Now that the only user is the generic zswap LRU reclaimer, it can be
simplified: pass the pinned zswap_entry directly, and consolidate the
refcount management in the shrink function.
Link: https://lkml.kernel.org/r/20230612093815.133504-7-cerasuolodomenico@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Tested-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Now that all three zswap backends have removed their shrink code, it is
no longer necessary for the zpool interface to include shrink/writeback
endpoints.
Link: https://lkml.kernel.org/r/20230612093815.133504-6-cerasuolodomenico@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "mm: zswap: move writeback LRU from zpool to zswap", v3.
This series aims to improve the zswap reclaim mechanism by reorganizing
the LRU management. In the current implementation, the LRU is maintained
within each zpool driver, resulting in duplicated code across the three
drivers. The proposed change consists in moving the LRU management from
the individual implementations up to the zswap layer.
The primary objective of this refactoring effort is to simplify the
codebase. By unifying the reclaim loop and consolidating LRU handling
within zswap, we can eliminate redundant code and improve
maintainability. Additionally, this change enables the reclamation of
stored pages in their actual LRU order. Presently, the zpool drivers
link backing pages in an LRU, causing compressed pages with different
LRU positions to be written back simultaneously.
The series consists of several patches. The first patch implements the
LRU and the reclaim loop in zswap, but it is not used yet because all
three driver implementations are marked as zpool_evictable.
The following three commits modify each zpool driver to be not
zpool_evictable, allowing the use of the reclaim loop in zswap.
As the drivers removed their shrink functions, the zpool interface is
then trimmed by removing zpool_evictable, zpool_ops, and zpool_shrink.
Finally, the code in zswap is further cleaned up by simplifying the
writeback function and removing the now unnecessary zswap_header.
This patch (of 7):
Each zpool driver (zbud, z3fold and zsmalloc) implements its own shrink
function, which is called from zpool_shrink. However, with this commit, a
unified shrink function is added to zswap. The ultimate goal is to
eliminate the need for zpool_shrink once all zpool implementations have
dropped their shrink code.
To ensure the functionality of each commit, this change focuses solely on
adding the mechanism itself. No modifications are made to the backends,
meaning that functionally, there are no immediate changes. The zswap
mechanism will only come into effect once the backends have removed their
shrink code. The subsequent commits will address the modifications needed
in the backends.
Link: https://lkml.kernel.org/r/20230612093815.133504-1-cerasuolodomenico@gmail.com
Link: https://lkml.kernel.org/r/20230612093815.133504-2-cerasuolodomenico@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Tested-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Commit 71024cb4a0bf ("frontswap: remove frontswap_tmem_exclusive_gets")
removed support for exclusive loads from frontswap as it was not used.
Bring back exclusive loads support to frontswap by adding an "exclusive"
output parameter to frontswap_ops->load.
On the zswap side, add a module parameter to enable/disable exclusive
loads, and a config option to control the boot default value. Refactor
zswap entry invalidation in zswap_frontswap_invalidate_page() into
zswap_invalidate_entry() to reuse it in zswap_frontswap_load() if
exclusive loads are enabled.
With exclusive loads, we avoid having two copies of the same page in
memory (compressed & uncompressed) after faulting it in from zswap. On
the other hand, if the page is to be reclaimed again without being
dirtied, it will be re-compressed. Compression is not usually slow, and a
page that was just faulted in is less likely to be reclaimed again soon.
Link: https://lkml.kernel.org/r/20230607195143.1473802-1-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Yu Zhao <yuzhao@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Before storing a page, zswap first checks if the number of stored pages
exceeds the limit specified by memory.zswap.max, for each cgroup in the
hierarchy. If this limit is reached or exceeded, then zswap shrinking is
triggered and short-circuits the store attempt.
However, since the zswap's LRU is not memcg-aware, this can create the
following pathological behavior: the cgroup whose zswap limit is 0 will
evict pages from other cgroups continually, without lowering its own zswap
usage. This means the shrinking will continue until the need for swap
ceases or the pool becomes empty.
As a result of this, we observe a disproportionate amount of zswap
writeback and a perpetually small zswap pool in our experiments, even
though the pool limit is never hit.
More generally, a cgroup might unnecessarily evict pages from other
cgroups before we drive the memcg back below its limit.
This patch fixes the issue by rejecting zswap store attempt without
shrinking the pool when obj_cgroup_may_zswap() returns false.
[akpm@linux-foundation.org: fix return of unintialized value]
[akpm@linux-foundation.org: s/ENOSPC/ENOMEM/]
Link: https://lkml.kernel.org/r/20230530222440.2777700-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20230530232435.3097106-1-nphamcs@gmail.com
Fixes: f4840ccfca25 ("zswap: memcg accounting")
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
This update addresses an issue with the zswap reclaim mechanism, which
hinders the efficient offloading of cold pages to disk, thereby
compromising the preservation of the LRU order and consequently
diminishing, if not inverting, its performance benefits.
The functioning of the zswap shrink worker was found to be inadequate, as
shown by basic benchmark test. For the test, a kernel build was utilized
as a reference, with its memory confined to 1G via a cgroup and a 5G swap
file provided. The results are presented below, these are averages of
three runs without the use of zswap:
real 46m26s
user 35m4s
sys 7m37s
With zswap (zbud) enabled and max_pool_percent set to 1 (in a 32G
system), the results changed to:
real 56m4s
user 35m13s
sys 8m43s
written_back_pages: 18
reject_reclaim_fail: 0
pool_limit_hit:1478
Besides the evident regression, one thing to notice from this data is the
extremely low number of written_back_pages and pool_limit_hit.
The pool_limit_hit counter, which is increased in zswap_frontswap_store
when zswap is completely full, doesn't account for a particular scenario:
once zswap hits his limit, zswap_pool_reached_full is set to true; with
this flag on, zswap_frontswap_store rejects pages if zswap is still above
the acceptance threshold. Once we include the rejections due to
zswap_pool_reached_full && !zswap_can_accept(), the number goes from 1478
to a significant 21578266.
Zswap is stuck in an undesirable state where it rejects pages because it's
above the acceptance threshold, yet fails to attempt memory reclaimation.
This happens because the shrink work is only queued when
zswap_frontswap_store detects that it's full and the work itself only
reclaims one page per run.
This state results in hot pages getting written directly to disk, while
cold ones remain memory, waiting only to be invalidated. The LRU order is
completely broken and zswap ends up being just an overhead without
providing any benefits.
This commit applies 2 changes: a) the shrink worker is set to reclaim
pages until the acceptance threshold is met and b) the task is also
enqueued when zswap is not full but still above the threshold.
Testing this suggested update showed much better numbers:
real 36m37s
user 35m8s
sys 9m32s
written_back_pages: 10459423
reject_reclaim_fail: 12896
pool_limit_hit: 75653
Link: https://lkml.kernel.org/r/20230526183227.793977-1-cerasuolodomenico@gmail.com
Fixes: 45190f01dd40 ("mm/zswap.c: add allocation hysteresis if pool limit is hit")
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The zswap writeback mechanism can cause a race condition resulting in
memory corruption, where a swapped out page gets swapped in with data that
was written to a different page.
The race unfolds like this:
1. a page with data A and swap offset X is stored in zswap
2. page A is removed off the LRU by zpool driver for writeback in
zswap-shrink work, data for A is mapped by zpool driver
3. user space program faults and invalidates page entry A, offset X is
considered free
4. kswapd stores page B at offset X in zswap (zswap could also be
full, if so, page B would then be IOed to X, then skip step 5.)
5. entry A is replaced by B in tree->rbroot, this doesn't affect the
local reference held by zswap-shrink work
6. zswap-shrink work writes back A at X, and frees zswap entry A
7. swapin of slot X brings A in memory instead of B
The fix:
Once the swap page cache has been allocated (case ZSWAP_SWAPCACHE_NEW),
zswap-shrink work just checks that the local zswap_entry reference is
still the same as the one in the tree. If it's not the same it means that
it's either been invalidated or replaced, in both cases the writeback is
aborted because the local entry contains stale data.
Reproducer:
I originally found this by running `stress` overnight to validate my work
on the zswap writeback mechanism, it manifested after hours on my test
machine. The key to make it happen is having zswap writebacks, so
whatever setup pumps /sys/kernel/debug/zswap/written_back_pages should do
the trick.
In order to reproduce this faster on a vm, I setup a system with ~100M of
available memory and a 500M swap file, then running `stress --vm 1
--vm-bytes 300000000 --vm-stride 4000` makes it happen in matter of tens
of minutes. One can speed things up even more by swinging
/sys/module/zswap/parameters/max_pool_percent up and down between, say, 20
and 1; this makes it reproduce in tens of seconds. It's crucial to set
`--vm-stride` to something other than 4096 otherwise `stress` won't
realize that memory has been corrupted because all pages would have the
same data.
Link: https://lkml.kernel.org/r/20230503151200.19707-1-cerasuolodomenico@gmail.com
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Chris Li (Google) <chrisl@kernel.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
- Nick Piggin's "shoot lazy tlbs" series, to improve the peformance of
switching from a user process to a kernel thread.
- More folio conversions from Kefeng Wang, Zhang Peng and Pankaj
Raghav.
- zsmalloc performance improvements from Sergey Senozhatsky.
- Yue Zhao has found and fixed some data race issues around the
alteration of memcg userspace tunables.
- VFS rationalizations from Christoph Hellwig:
- removal of most of the callers of write_one_page()
- make __filemap_get_folio()'s return value more useful
- Luis Chamberlain has changed tmpfs so it no longer requires swap
backing. Use `mount -o noswap'.
- Qi Zheng has made the slab shrinkers operate locklessly, providing
some scalability benefits.
- Keith Busch has improved dmapool's performance, making part of its
operations O(1) rather than O(n).
- Peter Xu adds the UFFD_FEATURE_WP_UNPOPULATED feature to userfaultd,
permitting userspace to wr-protect anon memory unpopulated ptes.
- Kirill Shutemov has changed MAX_ORDER's meaning to be inclusive
rather than exclusive, and has fixed a bunch of errors which were
caused by its unintuitive meaning.
- Axel Rasmussen give userfaultfd the UFFDIO_CONTINUE_MODE_WP feature,
which causes minor faults to install a write-protected pte.
- Vlastimil Babka has done some maintenance work on vma_merge():
cleanups to the kernel code and improvements to our userspace test
harness.
- Cleanups to do_fault_around() by Lorenzo Stoakes.
- Mike Rapoport has moved a lot of initialization code out of various
mm/ files and into mm/mm_init.c.
- Lorenzo Stoakes removd vmf_insert_mixed_prot(), which was added for
DRM, but DRM doesn't use it any more.
- Lorenzo has also coverted read_kcore() and vread() to use iterators
and has thereby removed the use of bounce buffers in some cases.
- Lorenzo has also contributed further cleanups of vma_merge().
- Chaitanya Prakash provides some fixes to the mmap selftesting code.
- Matthew Wilcox changes xfs and afs so they no longer take sleeping
locks in ->map_page(), a step towards RCUification of pagefaults.
- Suren Baghdasaryan has improved mmap_lock scalability by switching to
per-VMA locking.
- Frederic Weisbecker has reworked the percpu cache draining so that it
no longer causes latency glitches on cpu isolated workloads.
- Mike Rapoport cleans up and corrects the ARCH_FORCE_MAX_ORDER Kconfig
logic.
- Liu Shixin has changed zswap's initialization so we no longer waste a
chunk of memory if zswap is not being used.
- Yosry Ahmed has improved the performance of memcg statistics
flushing.
- David Stevens has fixed several issues involving khugepaged,
userfaultfd and shmem.
- Christoph Hellwig has provided some cleanup work to zram's IO-related
code paths.
- David Hildenbrand has fixed up some issues in the selftest code's
testing of our pte state changing.
- Pankaj Raghav has made page_endio() unneeded and has removed it.
- Peter Xu contributed some rationalizations of the userfaultfd
selftests.
- Yosry Ahmed has fixed an issue around memcg's page recalim
accounting.
- Chaitanya Prakash has fixed some arm-related issues in the
selftests/mm code.
- Longlong Xia has improved the way in which KSM handles hwpoisoned
pages.
- Peter Xu fixes a few issues with uffd-wp at fork() time.
- Stefan Roesch has changed KSM so that it may now be used on a
per-process and per-cgroup basis.
* tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (369 commits)
mm,unmap: avoid flushing TLB in batch if PTE is inaccessible
shmem: restrict noswap option to initial user namespace
mm/khugepaged: fix conflicting mods to collapse_file()
sparse: remove unnecessary 0 values from rc
mm: move 'mmap_min_addr' logic from callers into vm_unmapped_area()
hugetlb: pte_alloc_huge() to replace huge pte_alloc_map()
maple_tree: fix allocation in mas_sparse_area()
mm: do not increment pgfault stats when page fault handler retries
zsmalloc: allow only one active pool compaction context
selftests/mm: add new selftests for KSM
mm: add new KSM process and sysfs knobs
mm: add new api to enable ksm per process
mm: shrinkers: fix debugfs file permissions
mm: don't check VMA write permissions if the PTE/PMD indicates write permissions
migrate_pages_batch: fix statistics for longterm pin retry
userfaultfd: use helper function range_in_vma()
lib/show_mem.c: use for_each_populated_zone() simplify code
mm: correct arg in reclaim_pages()/reclaim_clean_pages_from_list()
fs/buffer: convert create_page_buffers to folio_create_buffers
fs/buffer: add folio_create_empty_buffers helper
...
|
|
Since some users may not use zswap, the zswap_pool is wasted. Save memory
by delaying the initialization of zswap until enabled.
[liushixin2@huawei.com: fix some pattern problem suggested by Christoph]
Link: https://lkml.kernel.org/r/20230411093632.822290-4-liushixin2@huawei.com
Link: https://lkml.kernel.org/r/20230403121318.1876082-4-liushixin2@huawei.com
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The zswap_init_started variable name has a bit confusing. Actually, there
are three state: uninitialized, initial failed and initial succeed. Add a
new variable zswap_init_state to replace zswap_init_{started/failed}.
Link: https://lkml.kernel.org/r/20230403121318.1876082-3-liushixin2@huawei.com
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "Delay the initialization of zswap", v9.
In the initialization of zswap, about 18MB memory will be allocated for
zswap_pool. Since some users may not use zswap, the zswap_pool is wasted.
Save memory by delaying the initialization of zswap until enabled.
This patch (of 3):
Remove zswap_entry_cache_create and zswap_entry_cache_destroy and use
kmem_cache_* function directly.
Link: https://lkml.kernel.org/r/20230411093632.822290-1-liushixin2@huawei.com
Link: https://lkml.kernel.org/r/20230403121318.1876082-1-liushixin2@huawei.com
Link: https://lkml.kernel.org/r/20230403121318.1876082-2-liushixin2@huawei.com
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Since commit 8b41fc4454e ("kbuild: create modules.builtin without
Makefile.modbuiltin or tristate.conf"), MODULE_LICENSE declarations
are used to identify modules. As a consequence, uses of the macro
in non-modules will cause modprobe to misidentify their containing
object file as a module when it is not (false positives), and modprobe
might succeed rather than failing with a suitable error message.
So remove it in the files in this commit, none of which can be built as
modules.
Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
Suggested-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: linux-modules@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Hitomi Hasegawa <hasegawa-hitomi@fujitsu.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
|
|
The worst-case scenario on finding same element pages is that almost all
elements are same at the first glance but only last few elements are
different.
Since the same element tends to be grouped from the beginning of the
pages, if we check the first element with the last element before looping
through all elements, we might have some chances to quickly detect
non-same element pages.
1. Test is done under LG webOS TV (64-bit arch)
2. Dump the swap-out pages (~819200 pages)
3. Analyze the pages with simple test script which counts the iteration
number and measures the speed at off-line
Under 64-bit arch, the worst iteration count is PAGE_SIZE / 8 bytes = 512.
The speed is based on the time to consume page_same_filled() function
only. The result, on average, is listed as below:
Num of Iter Speed(MB/s)
Looping-Forward (Orig) 38 99265
Looping-Backward 36 102725
Last-element-check (This Patch) 33 125072
The result shows that the average iteration count decreases by 13% and the
speed increases by 25% with this patch. This patch does not increase the
overall time complexity, though.
I also ran simpler version which uses backward loop. Just looping
backward also makes some improvement, but less than this patch.
A similar change has already been made to zram in 90f82cbfe502 ("zram: try
to avoid worst-case scenario on same element pages").
Link: https://lkml.kernel.org/r/20230205190036.1730134-1-taejoon.song@lge.com
Signed-off-by: Taejoon Song <taejoon.song@lge.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Taejoon Song <taejoon.song@lge.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <yjay.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "Implement writeback for zsmalloc", v7.
Unlike other zswap allocators such as zbud or z3fold, zsmalloc currently
lacks the writeback mechanism. This means that when the zswap pool is
full, it will simply reject further allocations, and the pages will be
written directly to swap.
This series of patches implements writeback for zsmalloc. When the zswap
pool becomes full, zsmalloc will attempt to evict all the compressed
objects in the least-recently used zspages.
This patch (of 6):
zswap's customary lock order is tree->lock before pool->lock, because the
tree->lock protects the entries' refcount, and the free callbacks in the
backends acquire their respective pool locks to dispatch the backing
object. zsmalloc's map callback takes the pool lock, so zswap must not
grab the tree->lock while a handle is mapped. This currently only happens
during writeback, which isn't implemented for zsmalloc. In preparation
for it, move the tree->lock section out of the mapped entry section
Link: https://lkml.kernel.org/r/20221128191616.1261026-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20221128191616.1261026-2-nphamcs@gmail.com
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
zswap_frontswap_load() should be called from preemptible context (we even
call mutex_lock() there) and it does not look like we need to do
GFP_ATOMIC allocaion for temp buffer. The same applies to
zswap_writeback_entry().
Use GFP_KERNEL for temporary buffer allocation in both cases.
Link: https://lkml.kernel.org/r/Y3xCTr6ikbtcUr/y@google.com
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
The argument is always set to end_swap_bio_write, so remove the argument
and mark end_swap_bio_write static.
Link: https://lkml.kernel.org/r/20220811141741.660214-1-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Applications can currently escape their cgroup memory containment when
zswap is enabled. This patch adds per-cgroup tracking and limiting of
zswap backend memory to rectify this.
The existing cgroup2 memory.stat file is extended to show zswap statistics
analogous to what's in meminfo and vmstat. Furthermore, two new control
files, memory.zswap.current and memory.zswap.max, are added to allow
tuning zswap usage on a per-workload basis. This is important since not
all workloads benefit from zswap equally; some even suffer compared to
disk swap when memory contents don't compress well. The optimal size of
the zswap pool, and the threshold for writeback, also depends on the size
of the workload's warm set.
The implementation doesn't use a traditional page_counter transaction.
zswap is unconventional as a memory consumer in that we only know the
amount of memory to charge once expensive compression has occurred. If
zwap is disabled or the limit is already exceeded we obviously don't want
to compress page upon page only to reject them all. Instead, the limit is
checked against current usage, then we compress and charge. This allows
some limit overrun, but not enough to matter in practice.
[hannes@cmpxchg.org: fix for CONFIG_SLOB builds]
Link: https://lkml.kernel.org/r/YnwD14zxYjUJPc2w@cmpxchg.org
[hannes@cmpxchg.org: opt out of cgroups v1]
Link: https://lkml.kernel.org/r/Yn6it9mBYFA+/lTb@cmpxchg.org
Link: https://lkml.kernel.org/r/20220510152847.230957-7-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Currently it requires poking at debugfs to figure out the size and
population of the zswap cache on a host. There are no counters for reads
and writes against the cache. As a result, it's difficult to understand
zswap behavior on production systems.
Print zswap memory consumption and how many pages are zswapped out in
/proc/meminfo. Count zswapouts and zswapins in /proc/vmstat.
Link: https://lkml.kernel.org/r/20220510152847.230957-6-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "MM changes to improve swap-over-NFS support".
Assorted improvements for swap-via-filesystem.
This is a resend of these patches, rebased on current HEAD. The only
substantial changes is that swap_dirty_folio has replaced
swap_set_page_dirty.
Currently swap-via-fs (SWP_FS_OPS) doesn't work for any filesystem. It
has previously worked for NFS but that broke a few releases back. This
series changes to use a new ->swap_rw rather than ->readpage and
->direct_IO. It also makes other improvements.
There is a companion series already in linux-next which fixes various
issues with NFS. Once both series land, a final patch is needed which
changes NFS over to use ->swap_rw.
This patch (of 10):
Many functions declared in include/linux/swap.h are only used within mm/
Create a new "mm/swap.h" and move some of these declarations there.
Remove the redundant 'extern' from the function declarations.
[akpm@linux-foundation.org: mm/memory-failure.c needs mm/swap.h]
Link: https://lkml.kernel.org/r/164859751830.29473.5309689752169286816.stgit@noble.brown
Link: https://lkml.kernel.org/r/164859778120.29473.11725907882296224053.stgit@noble.brown
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: David Howells <dhowells@redhat.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Zswap has an ability to efficiently store same-value filled pages, which
can be turned on and off using the "same_filled_pages_enabled"
parameter.
However, there is currently no way to enable just this (lightweight)
functionality, while not making use of the whole compressed page storage
machinery.
Add a "non_same_filled_pages_enabled" parameter which allows disabling
handling of pages that aren't same-value filled. This way zswap can be
run in such lightweight same-value filled pages only mode.
Link: https://lkml.kernel.org/r/7dbafa963e8bab43608189abbe2067f4b9287831.1641247624.git.maciej.szmigiero@oracle.com
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
There is only a single instance of frontswap ops in the kernel, so
simplify the frontswap code by removing support for multiple operations.
Link: https://lkml.kernel.org/r/20211224062246.1258487-13-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
In the ZSWAP_SWAPCACHE_FAIL and ZSWAP_SWAPCACHE_EXIST case, we forgot to
call zpool_unmap_handle() when zpool can't sleep. And we might sleep in
zswap_get_swap_cache_page() while zpool can't sleep. To fix all of these,
zpool_unmap_handle() should be done before zswap_get_swap_cache_page()
when zpool can't sleep.
Link: https://lkml.kernel.org/r/20210522092242.3233191-4-linmiaohe@huawei.com
Fixes: fc6697a89f56 ("mm/zswap: add the flag can_sleep_mapped")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Tian Tao <tiantao6@hisilicon.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The buf mapped via zpool_map_handle() is only used to store compressed
page buffer and there is no information to extract from it. So we could
use ZPOOL_MM_WO instead to avoid unnecessary copy-in at map time.
Link: https://lkml.kernel.org/r/20210522092242.3233191-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Tian Tao <tiantao6@hisilicon.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Patch series "Cleanup and fixup for zswap".
This series contains cleanups to remove unused function and avoid
unnecessary copy-in at map time. Also this fixes two bugs in the function
zswap_writeback_entry(). More details can be found in the respective
changelogs.
This patch (of 3):
zswap_debugfs_exit() is unused, remove it.
Link: https://lkml.kernel.org/r/20210522092242.3233191-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210522092242.3233191-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
strlcpy is marked as deprecated in Documentation/process/deprecated.rst,
and there is no functional difference when the caller expects truncation
(when not checking the return value). strscpy is relatively better as
it also avoids scanning the whole source string.
Link: https://lkml.kernel.org/r/1614227981-20367-1-git-send-email-daizhiyuan@phytium.com.cn
Signed-off-by: Zhiyuan Dai <daizhiyuan@phytium.com.cn>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Patch series "Fix the compatibility of zsmalloc and zswap".
Patch #1 adds a flag to zpool, then zswap used to determine if zpool
drivers such as zbud/z3fold/zsmalloc will enter an atomic context after
mapping.
The difference between zbud/z3fold and zsmalloc is that zsmalloc requires
an atomic context that since its map function holds a preempt-disabled,
but zbud/z3fold don't require an atomic context. So patch #2 sets flag
sleep_mapped to true indicating that zbud/z3fold can sleep after mapping.
zsmalloc didn't support sleep after mapping, so don't set that flag to
true.
This patch (of 2):
Add a flag to zpool, named is "can_sleep_mapped", and have it set true for
zbud/z3fold, not set this flag for zsmalloc, so its default value is
false. Then zswap could go the current path if the flag is true; and if
it's false, copy data from src to a temporary buffer, then unmap the
handle, take the mutex, process the buffer instead of src to avoid
sleeping function called from atomic context.
[natechancellor@gmail.com: add return value in zswap_frontswap_load]
Link: https://lkml.kernel.org/r/20210121214804.926843-1-natechancellor@gmail.com
[tiantao6@hisilicon.com: fix potential memory leak]
Link: https://lkml.kernel.org/r/1611538365-51811-1-git-send-email-tiantao6@hisilicon.com
[colin.king@canonical.com: fix potential uninitialized pointer read on tmp]
Link: https://lkml.kernel.org/r/20210128141728.639030-1-colin.king@canonical.com
[tiantao6@hisilicon.com: fix variable 'entry' is uninitialized when used]
Link: https://lkml.kernel.org/r/1611223030-58346-1-git-send-email-tiantao6@hisilicon.comLink: https://lkml.kernel.org/r/1611035683-12732-1-git-send-email-tiantao6@hisilicon.com
Link: https://lkml.kernel.org/r/1611035683-12732-2-git-send-email-tiantao6@hisilicon.com
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: Mike Galbraith <efault@gmx.de>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Correct wording and change one duplicated word (it) to "it is".
Link: https://lkml.kernel.org/r/20201221042848.13980-1-rdunlap@infradead.org
Fixes: 0ab0abcf5115 ("mm/zswap: refactor the get/put routines")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Weijie Yang <weijie.yang@samsung.com>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Right now, all new ZIP drivers are adapted to crypto_acomp APIs rather
than legacy crypto_comp APIs. Tradiontal ZIP drivers like lz4,lzo etc
have been also wrapped into acomp via scomp backend. But zswap.c is still
using the old APIs. That means zswap won't be able to work on any new ZIP
drivers in kernel.
This patch moves to use cryto_acomp APIs to fix the disconnected bridge
between new ZIP drivers and zswap. It is probably the first real user to
use acomp but perhaps not a good example to demonstrate how multiple acomp
requests can be executed in parallel in one acomp instance. frontswap is
doing page load and store page by page synchronously. swap_writepage()
depends on the completion of frontswap_store() to decide if it should call
__swap_writepage() to swap to disk.
However this patch creates multiple acomp instances, so multiple threads
running on multiple different cpus can actually do (de)compression
parallelly, leveraging the power of multiple ZIP hardware queues. This is
also consistent with frontswap's page management model.
The old zswap code uses atomic context and avoids the race conditions
while shared resources like zswap_dstmem are accessed. Here since acomp
can sleep, per-cpu mutex is used to replace preemption-disable.
While it is possible to make mm/page_io.c and mm/frontswap.c support async
(de)compression in some way, the entire design requires careful thinking
and performance evaluation. For the first step, the base with fixed
connection between ZIP drivers and zswap should be built.
Link: https://lkml.kernel.org/r/20201107065332.26992-1-song.bao.hua@hisilicon.com
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
Cc: Mahipal Challa <mahipalreddy2006@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Zhou Wang <wangzhou1@hisilicon.com>
Cc: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Fix smatch warning:
mm/zswap.c:425 zswap_cpu_comp_prepare() warn: passing zero to 'PTR_ERR'
crypto_alloc_comp() never return NULL, use IS_ERR instead of
IS_ERR_OR_NULL to fix this.
Link: https://lkml.kernel.org/r/20201031055615.28080-1-yuehaibing@huawei.com
Fixes: f1c54846ee45 ("zswap: dynamic pool creation")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
These should be const, so make it so.
Link: https://lkml.kernel.org/r/1791535ee0b00f4a5c68cc4a8adada06593ad8f1.1601770305.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The compressed cache for swap pages (zswap) currently needs from 1 to 3
extra kernel command line parameters in order to make it work: it has to
be enabled by adding a "zswap.enabled=1" command line parameter and if one
wants a different compressor or pool allocator than the default lzo / zbud
combination then these choices also need to be specified on the kernel
command line in additional parameters.
Using a different compressor and allocator for zswap is actually pretty
common as guides often recommend using the lz4 / z3fold pair instead of
the default one. In such case it is also necessary to remember to enable
the appropriate compression algorithm and pool allocator in the kernel
config manually.
Let's avoid the need for adding these kernel command line parameters and
automatically pull in the dependencies for the selected compressor
algorithm and pool allocator by adding an appropriate default switches to
Kconfig.
The default values for these options match what the code was using
previously as its defaults.
Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Link: http://lkml.kernel.org/r/20200202000112.456103-1-mail@maciej.szmigiero.name
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The "pool" pointer can be NULL at the end of the init_zswap(). (We
would allocate a new pool later in that situation)
So in the error handling then we need to make sure pool is a valid
pointer before calling "zswap_pool_destroy(pool);" because that function
dereferences the argument.
Link: http://lkml.kernel.org/r/20200114050902.og32fkllkod5ycf5@kili.mountain
Fixes: 93d4dfa9fbd0 ("mm/zswap.c: add allocation hysteresis if pool limit is hit")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
zswap will always try to shrink pool when zswap is full. If there is a
high pressure on zswap it will result in flipping pages in and out zswap
pool without any real benefit, and the overall system performance will
drop. The previous discussion on this subject [1] ended up with a
suggestion to implement a sort of hysteresis to refuse taking pages into
zswap pool until it has sufficient space if the limit has been hit.
This is my take on this.
Hysteresis is controlled with a sysfs-configurable parameter (namely,
/sys/kernel/debug/zswap/accept_threhsold_percent). It specifies the
threshold at which zswap would start accepting pages again after it
became full. Setting this parameter to 100 disables the hysteresis and
sets the zswap behavior to pre-hysteresis state.
[1] https://lkml.org/lkml/2019/11/8/949
Link: http://lkml.kernel.org/r/20200108200118.15563-1-vitaly.wool@konsulko.com
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
zswap_writeback_entry() maps a handle to read swpentry first, and
then in the most common case it would map the same handle again.
This is ok when zbud is the backend since its mapping callback is
plain and simple, but it slows things down for z3fold.
Since there's hardly a point in unmapping a handle _that_ fast as
zswap_writeback_entry() does when it reads swpentry, the
suggestion is to keep the handle mapped till the end.
Link: http://lkml.kernel.org/r/20190916004640.b453167d3556c4093af4cf7d@gmail.com
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Reviewed-by: Dan Streetman <ddstreet@ieee.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
This is the third version that was updated according to the comments from
Sergey Senozhatsky https://lkml.org/lkml/2019/5/29/73 and Shakeel Butt
https://lkml.org/lkml/2019/6/4/973
zswap compresses swap pages into a dynamically allocated RAM-based memory
pool. The memory pool should be zbud, z3fold or zsmalloc. All of them
will allocate unmovable pages. It will increase the number of unmovable
page blocks that will bad for anti-fragment.
zsmalloc support page migration if request movable page:
handle = zs_malloc(zram->mem_pool, comp_len,
GFP_NOIO | __GFP_HIGHMEM |
__GFP_MOVABLE);
And commit "zpool: Add malloc_support_movable to zpool_driver" add
zpool_malloc_support_movable check malloc_support_movable to make sure if
a zpool support allocate movable memory.
This commit let zswap allocate block with gfp
__GFP_HIGHMEM | __GFP_MOVABLE if zpool support allocate movable memory.
Following part is test log in a pc that has 8G memory and 2G swap.
Without this commit:
~# echo lz4 > /sys/module/zswap/parameters/compressor
~# echo zsmalloc > /sys/module/zswap/parameters/zpool
~# echo 1 > /sys/module/zswap/parameters/enabled
~# swapon /swapfile
~# cd /home/teawater/kernel/vm-scalability/
/home/teawater/kernel/vm-scalability# export unit_size=$((9 * 1024 * 1024 * 1024))
/home/teawater/kernel/vm-scalability# ./case-anon-w-seq
2717908992 bytes / 4826062 usecs = 549973 KB/s
2717908992 bytes / 4864201 usecs = 545661 KB/s
2717908992 bytes / 4867015 usecs = 545346 KB/s
2717908992 bytes / 4915485 usecs = 539968 KB/s
397853 usecs to free memory
357820 usecs to free memory
421333 usecs to free memory
420454 usecs to free memory
/home/teawater/kernel/vm-scalability# cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512
Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 1 1 1 0 2 1 1 0 1 0 0
Node 0, zone DMA, type Movable 0 0 0 0 0 0 0 0 0 1 3
Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Unmovable 6 5 8 6 6 5 4 1 1 1 0
Node 0, zone DMA32, type Movable 25 20 20 19 22 15 14 11 11 5 767
Node 0, zone DMA32, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Unmovable 4753 5588 5159 4613 3712 2520 1448 594 188 11 0
Node 0, zone Normal, type Movable 16 3 457 2648 2143 1435 860 459 223 224 296
Node 0, zone Normal, type Reclaimable 0 0 44 38 11 2 0 0 0 0 0
Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Number of blocks type Unmovable Movable Reclaimable HighAtomic CMA Isolate
Node 0, zone DMA 1 7 0 0 0 0
Node 0, zone DMA32 4 1652 0 0 0 0
Node 0, zone Normal 931 1485 15 0 0 0
With this commit:
~# echo lz4 > /sys/module/zswap/parameters/compressor
~# echo zsmalloc > /sys/module/zswap/parameters/zpool
~# echo 1 > /sys/module/zswap/parameters/enabled
~# swapon /swapfile
~# cd /home/teawater/kernel/vm-scalability/
/home/teawater/kernel/vm-scalability# export unit_size=$((9 * 1024 * 1024 * 1024))
/home/teawater/kernel/vm-scalability# ./case-anon-w-seq
2717908992 bytes / 4689240 usecs = 566020 KB/s
2717908992 bytes / 4760605 usecs = 557535 KB/s
2717908992 bytes / 4803621 usecs = 552543 KB/s
2717908992 bytes / 5069828 usecs = 523530 KB/s
431546 usecs to free memory
383397 usecs to free memory
456454 usecs to free memory
224487 usecs to free memory
/home/teawater/kernel/vm-scalability# cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512
Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 1 1 1 0 2 1 1 0 1 0 0
Node 0, zone DMA, type Movable 0 0 0 0 0 0 0 0 0 1 3
Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Unmovable 10 8 10 9 10 4 3 2 3 0 0
Node 0, zone DMA32, type Movable 18 12 14 16 16 11 9 5 5 6 775
Node 0, zone DMA32, type Reclaimable 0 0 0 0 0 0 0 0 0 0 1
Node 0, zone DMA32, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Unmovable 2669 1236 452 118 37 14 4 1 2 3 0
Node 0, zone Normal, type Movable 3850 6086 5274 4327 3510 2494 1520 934 438 220 470
Node 0, zone Normal, type Reclaimable 56 93 155 124 47 31 17 7 3 0 0
Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type CMA 0 0 0 0 0 0 0 0 0 0 0
Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0
Number of blocks type Unmovable Movable Reclaimable HighAtomic CMA Isolate
Node 0, zone DMA 1 7 0 0 0 0
Node 0, zone DMA32 4 1650 2 0 0 0
Node 0, zone Normal 79 2326 26 0 0 0
You can see that the number of unmovable page blocks is decreased
when the kernel has this commit.
Link: http://lkml.kernel.org/r/20190605100630.13293-2-teawaterz@linux.alibaba.com
Signed-off-by: Hui Zhu <teawaterz@linux.alibaba.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
When calling debugfs functions, there is no need to ever check the
return value. The function can work or not, but the code logic should
never do something different based on this.
Cc: Seth Jennings <sjenning@redhat.com>
Cc: linux-mm@kvack.org
Acked-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
Based on 3 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version [author] [kishon] [vijay] [abraham]
[i] [kishon]@[ti] [com] this program is distributed in the hope that
it will be useful but without any warranty without even the implied
warranty of merchantability or fitness for a particular purpose see
the gnu general public license for more details
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version [author] [graeme] [gregory]
[gg]@[slimlogic] [co] [uk] [author] [kishon] [vijay] [abraham] [i]
[kishon]@[ti] [com] [based] [on] [twl6030]_[usb] [c] [author] [hema]
[hk] [hemahk]@[ti] [com] this program is distributed in the hope
that it will be useful but without any warranty without even the
implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 1105 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.202006027@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
totalram_pages and totalhigh_pages are made static inline function.
Main motivation was that managed_page_count_lock handling was complicating
things. It was discussed in length here,
https://lore.kernel.org/patchwork/patch/995739/#1181785 So it seemes
better to remove the lock and convert variables to atomic, with preventing
poteintial store-to-read tearing as a bonus.
[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/1542090790-21750-4-git-send-email-arunks@codeaurora.org
Signed-off-by: Arun KS <arunks@codeaurora.org>
Suggested-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
/sys/../zswap/stored_pages keeps rising in a zswap test with
"zswap.max_pool_percent=0" parameter. But it should not compress or
store pages any more since there is no space in the compressed pool.
Reproduce steps:
1. Boot kernel with "zswap.enabled=1"
2. Set the max_pool_percent to 0
# echo 0 > /sys/module/zswap/parameters/max_pool_percent
3. Do memory stress test to see if some pages have been compressed
# stress --vm 1 --vm-bytes $mem_available"M" --timeout 60s
4. Watching the 'stored_pages' number increasing or not
The root cause is:
When zswap_max_pool_percent is set to 0 via kernel parameter,
zswap_is_full() will always return true due to zswap_shrink(). But if
the shinking is able to reclain a page successfully the code then
proceeds to compressing/storing another page, so the value of
stored_pages will keep changing.
To solve the issue, this patch adds a zswap_is_full() check again after
zswap_shrink() to make sure it's now under the max_pool_percent, and to
not compress/store if we reached the limit.
Link: http://lkml.kernel.org/r/20180530103936.17812-1-liwang@redhat.com
Signed-off-by: Li Wang <liwang@redhat.com>
Acked-by: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Huang Ying <huang.ying.caritas@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
mm/*.c files use symbolic and octal styles for permissions.
Using octal and not symbolic permissions is preferred by many as more
readable.
https://lkml.org/lkml/2016/8/2/1945
Prefer the direct use of octal for permissions.
Done using
$ scripts/checkpatch.pl -f --types=SYMBOLIC_PERMS --fix-inplace mm/*.c
and some typing.
Before: $ git grep -P -w "0[0-7]{3,3}" mm | wc -l
44
After: $ git grep -P -w "0[0-7]{3,3}" mm | wc -l
86
Miscellanea:
o Whitespace neatening around these conversions.
Link: http://lkml.kernel.org/r/2e032ef111eebcd4c5952bae86763b541d373469.1522102887.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
It was reported by Sergey Senozhatsky that if THP (Transparent Huge
Page) and frontswap (via zswap) are both enabled, when memory goes low
so that swap is triggered, segfault and memory corruption will occur in
random user space applications as follow,
kernel: urxvt[338]: segfault at 20 ip 00007fc08889ae0d sp 00007ffc73a7fc40 error 6 in libc-2.26.so[7fc08881a000+1ae000]
#0 0x00007fc08889ae0d _int_malloc (libc.so.6)
#1 0x00007fc08889c2f3 malloc (libc.so.6)
#2 0x0000560e6004bff7 _Z14rxvt_wcstoutf8PKwi (urxvt)
#3 0x0000560e6005e75c n/a (urxvt)
#4 0x0000560e6007d9f1 _ZN16rxvt_perl_interp6invokeEP9rxvt_term9hook_typez (urxvt)
#5 0x0000560e6003d988 _ZN9rxvt_term9cmd_parseEv (urxvt)
#6 0x0000560e60042804 _ZN9rxvt_term6pty_cbERN2ev2ioEi (urxvt)
#7 0x0000560e6005c10f _Z17ev_invoke_pendingv (urxvt)
#8 0x0000560e6005cb55 ev_run (urxvt)
#9 0x0000560e6003b9b9 main (urxvt)
#10 0x00007fc08883af4a __libc_start_main (libc.so.6)
#11 0x0000560e6003f9da _start (urxvt)
After bisection, it was found the first bad commit is bd4c82c22c36 ("mm,
THP, swap: delay splitting THP after swapped out").
The root cause is as follows:
When the pages are written to swap device during swapping out in
swap_writepage(), zswap (fontswap) is tried to compress the pages to
improve performance. But zswap (frontswap) will treat THP as a normal
page, so only the head page is saved. After swapping in, tail pages
will not be restored to their original contents, causing memory
corruption in the applications.
This is fixed by refusing to save page in the frontswap store functions
if the page is a THP. So that the THP will be swapped out to swap
device.
Another choice is to split THP if frontswap is enabled. But it is found
that the frontswap enabling isn't flexible. For example, if
CONFIG_ZSWAP=y (cannot be module), frontswap will be enabled even if
zswap itself isn't enabled.
Frontswap has multiple backends, to make it easy for one backend to
enable THP support, the THP checking is put in backend frontswap store
functions instead of the general interfaces.
Link: http://lkml.kernel.org/r/20180209084947.22749-1-ying.huang@intel.com
Fixes: bd4c82c22c367e068 ("mm, THP, swap: delay splitting THP after swapped out")
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Suggested-by: Minchan Kim <minchan@kernel.org> [put THP checking in backend]
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Shaohua Li <shli@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: <stable@vger.kernel.org> [4.14]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
We waste sizeof(swp_entry_t) for zswap header when using zsmalloc as
zpool driver because zsmalloc doesn't support eviction.
Add zpool_evictable() to detect if zpool is potentially evictable, and
use it in zswap to avoid waste memory for zswap header.
[yuzhao@google.com: The zpool->" prefix is a result of copy & paste]
Link: http://lkml.kernel.org/r/20180110225626.110330-1-yuzhao@google.com
Link: http://lkml.kernel.org/r/20180110224741.83751-1-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Acked-by: Dan Streetman <ddstreet@ieee.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Zswap is a cache which compresses the pages that are being swapped out
and stores them into a dynamically allocated RAM-based memory pool.
Experiments have shown that around 10-20% of pages stored in zswap are
same-filled pages (i.e. contents of the page are all same), but these
pages are handled as normal pages by compressing and allocating memory
in the pool.
This patch adds a check in zswap_frontswap_store() to identify
same-filled page before compression of the page. If the page is a
same-filled page, set zswap_entry.length to zero, save the same-filled
value and skip the compression of the page and alloction of memory in
zpool. In zswap_frontswap_load(), check if value of zswap_entry.length
is zero corresponding to the page to be loaded. If zswap_entry.length
is zero, fill the page with same-filled value. This saves the
decompression time during load.
On a ARM Quad Core 32-bit device with 1.5GB RAM by launching and
relaunching different applications, out of ~64000 pages stored in zswap,
~11000 pages were same-value filled pages (including zero-filled pages)
and ~9000 pages were zero-filled pages.
An average of 17% of pages(including zero-filled pages) in zswap are
same-value filled pages and 14% pages are zero-filled pages. An average
of 3% of pages are same-filled non-zero pages.
The below table shows the execution time profiling with the patch.
Baseline With patch % Improvement
-----------------------------------------------------------------
*Zswap Store Time 26.5ms 18ms 32%
(of same value pages)
*Zswap Load Time
(of same value pages) 25.5ms 13ms 49%
-----------------------------------------------------------------
On Ubuntu PC with 2GB RAM, while executing kernel build and other test
scripts and running multimedia applications, out of 360000 pages stored
in zswap 78000(~22%) of pages were found to be same-value filled pages
(including zero-filled pages) and 64000(~17%) are zero-filled pages. So
an average of %5 of pages are same-filled non-zero pages.
The below table shows the execution time profiling with the patch.
Baseline With patch % Improvement
-----------------------------------------------------------------
*Zswap Store Time 91ms 74ms 19%
(of same value pages)
*Zswap Load Time 50ms 7.5ms 85%
(of same value pages)
-----------------------------------------------------------------
*The execution times may vary with test device used.
Dan said:
: I did test this patch out this week, and I added some instrumentation to
: check the performance impact, and tested with a small program to try to
: check the best and worst cases.
:
: When doing a lot of swap where all (or almost all) pages are same-value, I
: found this patch does save both time and space, significantly. The exact
: improvement in time and space depends on which compressor is being used,
: but roughly agrees with the numbers you listed.
:
: In the worst case situation, where all (or almost all) pages have the
: same-value *except* the final long (meaning, zswap will check each long on
: the entire page but then still have to pass the page to the compressor),
: the same-value check is around 10-15% of the total time spent in
: zswap_frontswap_store(). That's a not-insignificant amount of time, but
: it's not huge. Considering that most systems will probably be swapping
: pages that aren't similar to the worst case (although I don't have any
: data to know that), I'd say the improvement is worth the possible
: worst-case performance impact.
[srividya.dr@samsung.com: add memset_l instead of for loop]
Link: http://lkml.kernel.org/r/20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p1
Signed-off-by: Srividya Desireddy <srividya.dr@samsung.com>
Acked-by: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Dinakar Reddy Pathireddy <dinakar.p@samsung.com>
Cc: SHARAN ALLUR <sharan.allur@samsung.com>
Cc: RAJIB BASU <rajib.basu@samsung.com>
Cc: JUHUN KIM <juhunkim@samsung.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Timofey Titovets <nefelim4ag@gmail.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
zswap_dstmem_prepare()
Omit an extra message for a memory allocation failure in this function.
This issue was detected by using the Coccinelle software.
Link: http://events.linuxfoundation.org/sites/events/files/slides/LCJ16-Refactor_Strings-WSang_0.pdf
Link: http://lkml.kernel.org/r/bae25b04-2ce2-7137-a71c-50d7b4f06431@users.sourceforge.net
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Replace the specification of a data structure by a pointer dereference
as the parameter for the operator "sizeof" to make the corresponding
size determination a bit safer according to the Linux coding style
convention.
Link: http://lkml.kernel.org/r/19f9da22-092b-f867-bdf6-f4dbad7ccf1f@users.sourceforge.net
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
zswap_pool_create()
Omit an extra message for a memory allocation failure in this function.
This issue was detected by using the Coccinelle software.
Link: http://events.linuxfoundation.org/sites/events/files/slides/LCJ16-Refactor_Strings-WSang_0.pdf
Link: http://lkml.kernel.org/r/2345aabc-ae98-1d31-afba-40a02c5baf3d@users.sourceforge.net
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Change the zpool/compressor param callback function to release the
zswap_pools_lock spinlock before calling param_set_charp, since that
function may sleep when it calls kmalloc with GFP_KERNEL.
While this problem has existed for a while, I wasn't able to trigger it
using a tight loop changing either/both the zpool and compressor params; I
think it's very unlikely to be an issue on the stable kernels, especially
since most zswap users will change the compressor and/or zpool from sysfs
only one time each boot - or zero times, if they add the params to the
kernel boot.
Fixes: c99b42c3529e ("zswap: use charp for zswap param strings")
Link: http://lkml.kernel.org/r/20170126155821.4545-1-ddstreet@ieee.org
Signed-off-by: Dan Streetman <dan.streetman@canonical.com>
Reported-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
If either the compressor and/or zpool param are invalid at boot, and
their default value is also invalid, set the param to the empty string
to indicate there is no compressor and/or zpool configured. This allows
users to check the sysfs interface to see which param needs changing.
Link: http://lkml.kernel.org/r/20170124200259.16191-4-ddstreet@ieee.org
Signed-off-by: Dan Streetman <dan.streetman@canonical.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Allow zswap to initialize at boot even if it can't create its pool due
to a failure to create a zpool and/or compressor. Allow those to be
created later, from the sysfs module param interface.
Link: http://lkml.kernel.org/r/20170124200259.16191-3-ddstreet@ieee.org
Signed-off-by: Dan Streetman <dan.streetman@canonical.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Add zswap_init_failed bool that prevents changing any of the module
params, if init_zswap() fails, and set zswap_enabled to false. Change
'enabled' param to a callback, and check zswap_init_failed before
allowing any change to 'enabled', 'zpool', or 'compressor' params.
Any driver that is built-in to the kernel will not be unloaded if its
init function returns error, and its module params remain accessible for
users to change via sysfs. Since zswap uses param callbacks, which
assume that zswap has been initialized, changing the zswap params after
a failed initialization will result in WARNING due to the param
callbacks expecting a pool to already exist. This prevents that by
immediately exiting any of the param callbacks if initialization failed.
This was reported here:
https://marc.info/?l=linux-mm&m=147004228125528&w=4
And fixes this WARNING:
[ 429.723476] WARNING: CPU: 0 PID: 5140 at mm/zswap.c:503 __zswap_pool_current+0x56/0x60
The warning is just noise, and not serious. However, when init fails,
zswap frees all its percpu dstmem pages and its kmem cache. The kmem
cache might be serious, if kmem_cache_alloc(NULL, gfp) has problems; but
the percpu dstmem pages are definitely a problem, as they're used as
temporary buffer for compressed pages before copying into place in the
zpool.
If the user does get zswap enabled after an init failure, then zswap
will likely Oops on the first page it tries to compress (or worse, start
corrupting memory).
Fixes: 90b0fc26d5db ("zswap: change zpool/compressor at runtime")
Link: http://lkml.kernel.org/r/20170124200259.16191-2-ddstreet@ieee.org
Signed-off-by: Dan Streetman <dan.streetman@canonical.com>
Reported-by: Marcin Miroslaw <marcin@mejor.pl>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Install the callbacks via the state machine. Multi state is used to address the
per-pool notifier. Uppon adding of the intance the callback is invoked for all
online CPUs so the manual init can go.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-mm@kvack.org
Cc: Seth Jennings <sjenning@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161126231350.10321-13-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-mm@kvack.org
Cc: Seth Jennings <sjenning@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161126231350.10321-12-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Add a work_struct to struct zswap_pool, and change __zswap_pool_empty to
use the workqueue instead of using call_rcu().
When zswap destroys a pool no longer in use, it uses call_rcu() to
perform the destruction/freeing. Since that executes in softirq
context, it must not sleep. However, actually destroying the pool
involves freeing the per-cpu compressors (which requires locking the
cpu_add_remove_lock mutex) and freeing the zpool, for which the
implementation may sleep (e.g. zsmalloc calls kmem_cache_destroy, which
locks the slab_mutex). So if either mutex is currently taken, or any
other part of the compressor or zpool implementation sleeps, it will
result in a BUG().
It's not easy to reproduce this when changing zswap's params normally.
In testing with a loaded system, this does not fail:
$ cd /sys/module/zswap/parameters
$ echo lz4 > compressor ; echo zsmalloc > zpool
nor does this:
$ while true ; do
> echo lzo > compressor ; echo zbud > zpool
> sleep 1
> echo lz4 > compressor ; echo zsmalloc > zpool
> sleep 1
> done
although it's still possible either of those might fail, depending on
whether anything else besides zswap has locked the mutexes.
However, changing a parameter with no delay immediately causes the
schedule while atomic BUG:
$ while true ; do
> echo lzo > compressor ; echo lz4 > compressor
> done
This is essentially the same as Yu Zhao's proposed patch to zsmalloc,
but moved to zswap, to cover compressor and zpool freeing.
Fixes: f1c54846ee45 ("zswap: dynamic pool creation")
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Reported-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Dan Streetman <dan.streetman@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Instead of using "zswap" as the name for all zpools created, add an
atomic counter and use "zswap%x" with the counter number for each zpool
created, to provide a unique name for each new zpool.
As zsmalloc, one of the zpool implementations, requires/expects a unique
name for each pool created, zswap should provide a unique name. The
zsmalloc pool creation does not fail if a new pool with a conflicting
name is created, unless CONFIG_ZSMALLOC_STAT is enabled; in that case,
zsmalloc pool creation fails with -ENOMEM. Then zswap will be unable to
change its compressor parameter if its zpool is zsmalloc; it also will
be unable to change its zpool parameter back to zsmalloc, if it has any
existing old zpool using zsmalloc with page(s) in it. Attempts to
change the parameters will result in failure to create the zpool. This
changes zswap to provide a unique name for each zpool creation.
Fixes: f1c54846ee45 ("zswap: dynamic pool creation")
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dan Streetman <dan.streetman@canonical.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time
ago with promise that one day it will be possible to implement page
cache with bigger chunks than PAGE_SIZE.
This promise never materialized. And unlikely will.
We have many places where PAGE_CACHE_SIZE assumed to be equal to
PAGE_SIZE. And it's constant source of confusion on whether
PAGE_CACHE_* or PAGE_* constant should be used in a particular case,
especially on the border between fs and mm.
Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
breakage to be doable.
Let's stop pretending that pages in page cache are special. They are
not.
The changes are pretty straight-forward:
- <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
- <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;
- PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};
- page_cache_get() -> get_page();
- page_cache_release() -> put_page();
This patch contains automated changes generated with coccinelle using
script below. For some reason, coccinelle doesn't patch header files.
I've called spatch for them manually.
The only adjustment after coccinelle is revert of changes to
PAGE_CAHCE_ALIGN definition: we are going to drop it later.
There are few places in the code where coccinelle didn't reach. I'll
fix them manually in a separate patch. Comments and documentation also
will be addressed with the separate patch.
virtual patch
@@
expression E;
@@
- E << (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E
@@
expression E;
@@
- E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT)
+ E
@@
@@
- PAGE_CACHE_SHIFT
+ PAGE_SHIFT
@@
@@
- PAGE_CACHE_SIZE
+ PAGE_SIZE
@@
@@
- PAGE_CACHE_MASK
+ PAGE_MASK
@@
expression E;
@@
- PAGE_CACHE_ALIGN(E)
+ PAGE_ALIGN(E)
@@
expression E;
@@
- page_cache_get(E)
+ get_page(E)
@@
expression E;
@@
- page_cache_release(E)
+ put_page(E)
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Change the use of strncmp in zswap_pool_find_get() to strcmp.
The use of strncmp is no longer correct, now that zswap_zpool_type is
not an array; sizeof() will return the size of a pointer, which isn't
the right length to compare. We don't need to use strncmp anyway,
because the existing params and the passed in params are all guaranteed
to be null terminated, so strcmp should be used.
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Reported-by: Weijie Yang <weijie.yang@samsung.com>
Cc: Seth Jennings <sjennings@variantweb.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Instead of using a fixed-length string for the zswap params, use charp.
This simplifies the code and uses less memory, as most zswap param strings
will be less than the current maximum length.
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Seth Jennings <sjennings@variantweb.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
On the next line entry variable will be re-initialized so no need to init
it with NULL.
Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
sleep and avoiding waking kswapd
__GFP_WAIT has been used to identify atomic context in callers that hold
spinlocks or are in interrupts. They are expected to be high priority and
have access one of two watermarks lower than "min" which can be referred
to as the "atomic reserve". __GFP_HIGH users get access to the first
lower watermark and can be called the "high priority reserve".
Over time, callers had a requirement to not block when fallback options
were available. Some have abused __GFP_WAIT leading to a situation where
an optimisitic allocation with a fallback option can access atomic
reserves.
This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
cannot sleep and have no alternative. High priority users continue to use
__GFP_HIGH. __GFP_DIRECT_RECLAIM identifies callers that can sleep and
are willing to enter direct reclaim. __GFP_KSWAPD_RECLAIM to identify
callers that want to wake kswapd for background reclaim. __GFP_WAIT is
redefined as a caller that is willing to enter direct reclaim and wake
kswapd for background reclaim.
This patch then converts a number of sites
o __GFP_ATOMIC is used by callers that are high priority and have memory
pools for those requests. GFP_ATOMIC uses this flag.
o Callers that have a limited mempool to guarantee forward progress clear
__GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
into this category where kswapd will still be woken but atomic reserves
are not used as there is a one-entry mempool to guarantee progress.
o Callers that are checking if they are non-blocking should use the
helper gfpflags_allow_blocking() where possible. This is because
checking for __GFP_WAIT as was done historically now can trigger false
positives. Some exceptions like dm-crypt.c exist where the code intent
is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
flag manipulations.
o Callers that built their own GFP flags instead of starting with GFP_KERNEL
and friends now also need to specify __GFP_KSWAPD_RECLAIM.
The first key hazard to watch out for is callers that removed __GFP_WAIT
and was depending on access to atomic reserves for inconspicuous reasons.
In some cases it may be appropriate for them to use __GFP_HIGH.
The second key hazard is callers that assembled their own combination of
GFP flags instead of starting with something like GFP_KERNEL. They may
now wish to specify __GFP_KSWAPD_RECLAIM. It's almost certainly harmless
if it's missed in most cases as other activity will wake kswapd.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Update the zpool and compressor parameters to be changeable at runtime.
When changed, a new pool is created with the requested zpool/compressor,
and added as the current pool at the front of the pool list. Previous
pools remain in the list only to remove existing compressed pages from.
The old pool(s) are removed once they become empty.
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Seth Jennings <sjennings@variantweb.net>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Add dynamic creation of pools. Move the static crypto compression per-cpu
transforms into each pool. Add a pointer to zswap_entry to the pool it's
in.
This is required by the following patch which enables changing the zswap
zpool and compressor params at runtime.
[akpm@linux-foundation.org: fix merge snafus]
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Seth Jennings <sjennings@variantweb.net>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The structure zpool_ops is not modified so make the pointer to it a
pointer to const.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Dan Streetman <ddstreet@ieee.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
zswap_get_swap_cache_page and read_swap_cache_async have pretty much the
same code with only significant difference in return value and usage of
swap_readpage.
I a helper __read_swap_cache_async() with the common code. Behavior
change: now zswap_get_swap_cache_page will use radix_tree_maybe_preload
instead radix_tree_preload. Looks like, this wasn't changed only by the
reason of code duplication.
Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Seth Jennings <sjennings@variantweb.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Change the "enabled" parameter to be configurable at runtime. Remove the
enabled check from init(), and move it to the frontswap store() function;
when enabled, pages will be stored, and when disabled, pages won't be
stored.
This is almost identical to Seth's patch from 2 years ago:
http://lkml.iu.edu/hypermail/linux/kernel/1307.2/04289.html
[akpm@linux-foundation.org: tweak documentation]
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Suggested-by: Seth Jennings <sjennings@variantweb.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
