- 06 Apr, 2023 19 commits
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Christoph Hellwig authored
Instead of returning NULL for all errors, distinguish between: - no entry found and not asked to allocated (-ENOENT) - failed to allocate memory (-ENOMEM) - would block (-EAGAIN) so that callers don't have to guess the error based on the passed in flags. Also pass through the error through the direct callers: filemap_get_folio, filemap_lock_folio filemap_grab_folio and filemap_get_incore_folio. [hch@lst.de: fix null-pointer deref] Link: https://lkml.kernel.org/r/20230310070023.GA13563@lst.de Link: https://lkml.kernel.org/r/20230310043137.GA1624890@u2004 Link: https://lkml.kernel.org/r/20230307143410.28031-8-hch@lst.deSigned-off-by:
Christoph Hellwig <hch@lst.de> Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com> [nilfs2] Cc: Andreas Gruenbacher <agruenba@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org>
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Christoph Hellwig authored
FGP_ENTRY is unused now, so remove it. Link: https://lkml.kernel.org/r/20230307143410.28031-7-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Use the very low level filemap_get_entry helper to look up the entry in the xarray, and then: - don't bother locking the folio if only doing a userfault notification - open code locking the page and checking for truncation in a related code block This will allow to eventually remove the FGP_ENTRY flag. [hughd@google.com: adjust the new comment line] Link: https://lkml.kernel.org/r/af178ebb-1076-a38c-1dc1-2a37ccce4a3@google.com Link: https://lkml.kernel.org/r/20230307143410.28031-6-hch@lst.deSigned-off-by:
Hugh Dickins <hughd@google.com> Acked-by:
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Hugh Dickins authored
To avoid use of the FGP_ENTRY flag, adapt shmem_get_partial_folio() to use filemap_get_entry() and folio_lock() instead of __filemap_get_folio(). Update "page" in the comments there to "folio". Link: https://lkml.kernel.org/r/9d1aaa4-1337-fb81-6f37-74ebc96f9ef@google.comSigned-off-by:
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Christoph Hellwig authored
filemap_get_incore_folio wants to look at the details of xa_is_value entries, but doesn't need any of the other logic in filemap_get_folio. Switch it to use the lower-level filemap_get_entry interface. Link: https://lkml.kernel.org/r/20230307143410.28031-4-hch@lst.deSigned-off-by:
Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Andreas Gruenbacher <agruenba@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com> Signed-off-by:
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Christoph Hellwig authored
mapping_get_entry is useful for page cache API users that need to know about xa_value internals. Rename it and make it available in pagemap.h. Link: https://lkml.kernel.org/r/20230307143410.28031-3-hch@lst.deSigned-off-by:
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Christoph Hellwig authored
Patch series "return an ERR_PTR from __filemap_get_folio", v3. __filemap_get_folio and its wrappers can return NULL for three different conditions, which in some cases requires the caller to reverse engineer the decision making. This is fixed by returning an ERR_PTR instead of NULL and thus transporting the reason for the failure. But to make that work we first need to ensure that no xa_value special case is returned and thus return the FGP_ENTRY flag. It turns out that flag is barely used and can usually be deal with in a better way. This patch (of 7): split_huge_pages_in_file never wants to do anything with the special value enties. Switch to using filemap_get_folio to not even see them. Link: https://lkml.kernel.org/r/20230307143410.28031-1-hch@lst.de Link: https://lkml.kernel.org/r/20230307143410.28031-2-hch@lst.deSigned-off-by:
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Keith Busch authored
Set the 'empty' bool directly from the result of the function that determines its value instead of adding additional logic. Link: https://lkml.kernel.org/r/20230126215125.4069751-13-kbusch@meta.comSigned-off-by:
Keith Busch <kbusch@kernel.org> Reviewed-by:
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Keith Busch authored
The allocated dmapool pages are never freed for the lifetime of the pool. There is no need for the two level list+stack lookup for finding a free block since nothing is ever removed from the list. Just use a simple stack, reducing time complexity to constant. The implementation inserts the stack linking elements and the dma handle of the block within itself when freed. This means the smallest possible dmapool block is increased to at most 16 bytes to accommodate these fields, but there are no exisiting users requesting a dma pool smaller than that anyway. Removing the list has a significant change in performance. Using the kernel's micro-benchmarking self test: Before: # modprobe dmapool_test dmapool test: size:16 blocks:8192 time:57282 dmapool test: size:64 blocks:8192 time:172562 dmapool test: size:256 blocks:8192 time:789247 dmapool test: size:1024 blocks:2048 time:371823 dmapool test: size:4096 blocks:1024 time:362237 After: # modprobe dmapool_test dmapool test: size:16 blocks:8192 time:24997 dmapool test: size:64 blocks:8192 time:26584 dmapool test: size:256 blocks:8192 time:33542 dmapool test: size:1024 blocks:2048 time:9022 dmapool test: size:4096 blocks:1024 time:6045 The module test allocates quite a few blocks that may not accurately represent how these pools are used in real life. For a more marco level benchmark, running fio high-depth + high-batched on nvme, this patch shows submission and completion latency reduced by ~100usec each, 1% IOPs improvement, and perf record's time spent in dma_pool_alloc/free were reduced by half. [kbusch@kernel.org: push new blocks in ascending order] Link: https://lkml.kernel.org/r/20230221165400.1595247-1-kbusch@meta.com Link: https://lkml.kernel.org/r/20230126215125.4069751-12-kbusch@meta.comSigned-off-by:
Bryan O'Donoghue <bryan.odonoghue@linaro.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Tony Battersby <tonyb@cybernetics.com> Signed-off-by:
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Keith Busch authored
If debug is enabled, dmapool will poison the range, so no need to clear it to 0 immediately before writing over it. Link: https://lkml.kernel.org/r/20230126215125.4069751-11-kbusch@meta.comSigned-off-by:
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Keith Busch authored
The actions for busy and not busy are mostly the same, so combine these and remove the unnecessary function. Also, the pool is about to be freed so there's no need to poison the page data since we only check for poison on alloc, which can't be done on a freed pool. Link: https://lkml.kernel.org/r/20230126215125.4069751-10-kbusch@meta.comSigned-off-by:
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Keith Busch authored
Various fields of the dma pool are set in different places. Move it all to one function. Link: https://lkml.kernel.org/r/20230126215125.4069751-9-kbusch@meta.comSigned-off-by:
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Keith Busch authored
Handle the error in a condition so the good path can be in the normal flow. Link: https://lkml.kernel.org/r/20230126215125.4069751-8-kbusch@meta.comSigned-off-by:
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Keith Busch authored
Clean up the normal path by moving the debug code outside it. Link: https://lkml.kernel.org/r/20230126215125.4069751-7-kbusch@meta.comSigned-off-by:
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Tony Battersby authored
Avoid double-memset of the same allocated memory in dma_pool_alloc() when both DMAPOOL_DEBUG is enabled and init_on_alloc=1. Link: https://lkml.kernel.org/r/20230126215125.4069751-6-kbusch@meta.comSigned-off-by:
Tony Battersby <tonyb@cybernetics.com> Signed-off-by:
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Tony Battersby authored
To represent the size of a single allocation, dmapool currently uses 'unsigned int' in some places and 'size_t' in other places. Standardize on 'unsigned int' to reduce overhead, but use 'size_t' when counting all the blocks in the entire pool. Link: https://lkml.kernel.org/r/20230126215125.4069751-5-kbusch@meta.comSigned-off-by:
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Tony Battersby authored
Use sysfs_emit instead of scnprintf, snprintf or sprintf. Link: https://lkml.kernel.org/r/20230126215125.4069751-4-kbusch@meta.comSigned-off-by:
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Tony Battersby authored
dmapool originally tried to support pools without a device because dma_alloc_coherent() supports allocations without a device. But nobody ended up using dma pools without a device, and trying to do so will result in an oops. So remove the checks for pool->dev == NULL since they are unneeded bloat. [kbusch@kernel.org: add check for null dev on create] Link: https://lkml.kernel.org/r/20230126215125.4069751-3-kbusch@meta.comSigned-off-by:
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Keith Busch authored
Patch series "dmapool enhancements", v4. Time spent in dma_pool alloc/free increases linearly with the number of pages backing the pool. We can reduce this to constant time with minor changes to how free pages are tracked. This patch (of 12): Provide a module that allocates and frees many blocks of various sizes and report how long it takes. This is intended to provide a consistent way to measure how changes to the dma_pool_alloc/free routines affect timing. Link: https://lkml.kernel.org/r/20230126215125.4069751-1-kbusch@meta.com Link: https://lkml.kernel.org/r/20230126215125.4069751-2-kbusch@meta.comSigned-off-by:
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- 28 Mar, 2023 21 commits
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Peter Xu authored
TRANSPARENT_HUGEPAGE_NEVER_DAX has nothing to do with DAX. It's set when has_transparent_hugepage() returns false, checked in hugepage_vma_check() and will disable THP completely if false. Rename it to TRANSPARENT_HUGEPAGE_UNSUPPORTED to reflect its real purpose. [peterx@redhat.com: fix comment, per David] Link: https://lkml.kernel.org/r/ZBMzQW674oHQJV7F@x1n Link: https://lkml.kernel.org/r/20230315171642.1244625-1-peterx@redhat.comSigned-off-by:
Peter Xu <peterx@redhat.com> Acked-by:
David Hildenbrand <david@redhat.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: Yang Shi <shy828301@gmail.com> Signed-off-by:
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Kefeng Wang authored
It's more clear and simple to just use IS_ENABLED(CONFIG_HWPOISON_INJECT) to check whether or not to enable HWPoison injector module instead of CONFIG_HWPOISON_INJECT/CONFIG_HWPOISON_INJECT_MODULE. Link: https://lkml.kernel.org/r/20230313053929.84607-1-wangkefeng.wang@huawei.comSigned-off-by:
Kefeng Wang <wangkefeng.wang@huawei.com> Reviewed-by:
Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Signed-off-by:
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Qi Zheng authored
Now there are no readers of shrinker_rwsem, so we can simply replace it with mutex lock. Link: https://lkml.kernel.org/r/20230313112819.38938-9-zhengqi.arch@bytedance.comSigned-off-by:
Qi Zheng <zhengqi.arch@bytedance.com> Acked-by:
Vlastimil Babka <vbabka@suse.cz> Acked-by:
Kirill Tkhai <tkhai@ya.ru> Acked-by:
Roman Gushchin <roman.gushchin@linux.dev> Cc: Christian König <christian.koenig@amd.com> Cc: David Hildenbrand <david@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Shakeel Butt <shakeelb@google.com> Cc: Sultan Alsawaf <sultan@kerneltoast.com> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Cc: Yang Shi <shy828301@gmail.com> Signed-off-by:
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Qi Zheng authored
Currently, the synchronize_shrinkers() is only used by TTM pool. It only requires that no shrinkers run in parallel, and doesn't care about registering and unregistering of shrinkers. Since slab shrink is protected by SRCU, synchronize_srcu() is sufficient to ensure that no shrinker is running in parallel. So the shrinker_rwsem in synchronize_shrinkers() is no longer needed, just remove it. Link: https://lkml.kernel.org/r/20230313112819.38938-8-zhengqi.arch@bytedance.comSigned-off-by:
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Qi Zheng authored
For now, reparent_shrinker_deferred() is the only holder of read lock of shrinker_rwsem. And it already holds the global cgroup_mutex, so it will not be called in parallel. Therefore, in order to convert shrinker_rwsem to shrinker_mutex later, here we change to hold the write lock of shrinker_rwsem to reparent. Link: https://lkml.kernel.org/r/20230313112819.38938-7-zhengqi.arch@bytedance.comSigned-off-by:
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Qi Zheng authored
Like global and memcg slab shrink, also use SRCU to make count and scan operations in memory shrinker debugfs lockless. Link: https://lkml.kernel.org/r/20230313112819.38938-6-zhengqi.arch@bytedance.comSigned-off-by:
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Kirill Tkhai authored
After we make slab shrink lockless with SRCU, the longest sleep unregister_shrinker() will be a sleep waiting for all do_shrink_slab() calls. To avoid long unbreakable action in the unregister_shrinker(), add shrinker_srcu_generation to restore a check similar to the rwsem_is_contendent() check that we had before. And for memcg slab shrink, we unlock SRCU and continue iterations from the next shrinker id. Link: https://lkml.kernel.org/r/20230313112819.38938-5-zhengqi.arch@bytedance.comSigned-off-by:
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Qi Zheng authored
Like global slab shrink, this commit also uses SRCU to make memcg slab shrink lockless. We can reproduce the down_read_trylock() hotspot through the following script: ``` DIR="/root/shrinker/memcg/mnt" do_create() { mkdir -p /sys/fs/cgroup/memory/test mkdir -p /sys/fs/cgroup/perf_event/test echo 4G > /sys/fs/cgroup/memory/test/memory.limit_in_bytes for i in `seq 0 $1`; do mkdir -p /sys/fs/cgroup/memory/test/$i; echo $$ > /sys/fs/cgroup/memory/test/$i/cgroup.procs; echo $$ > /sys/fs/cgroup/perf_event/test/cgroup.procs; mkdir -p $DIR/$i; done } do_mount() { for i in `seq $1 $2`; do mount -t tmpfs $i $DIR/$i; done } do_touch() { for i in `seq $1 $2`; do echo $$ > /sys/fs/cgroup/memory/test/$i/cgroup.procs; echo $$ > /sys/fs/cgroup/perf_event/test/cgroup.procs; dd if=/dev/zero of=$DIR/$i/file$i bs=1M count=1 & done } case "$1" in touch) do_touch $2 $3 ;; test) do_create 4000 do_mount 0 4000 do_touch 0 3000 ;; *) exit 1 ;; esac ``` Save the above script, then run test and touch commands. Then we can use the following perf command to view hotspots: perf top -U -F 999 1) Before applying this patchset: 32.31% [kernel] [k] down_read_trylock 19.40% [kernel] [k] pv_native_safe_halt 16.24% [kernel] [k] up_read 15.70% [kernel] [k] shrink_slab 4.69% [kernel] [k] _find_next_bit 2.62% [kernel] [k] shrink_node 1.78% [kernel] [k] shrink_lruvec 0.76% [kernel] [k] do_shrink_slab 2) After applying this patchset: 27.83% [kernel] [k] _find_next_bit 16.97% [kernel] [k] shrink_slab 15.82% [kernel] [k] pv_native_safe_halt 9.58% [kernel] [k] shrink_node 8.31% [kernel] [k] shrink_lruvec 5.64% [kernel] [k] do_shrink_slab 3.88% [kernel] [k] mem_cgroup_iter At the same time, we use the following perf command to capture IPC information: perf stat -e cycles,instructions -G test -a --repeat 5 -- sleep 10 1) Before applying this patchset: Performance counter stats for 'system wide' (5 runs): 454187219766 cycles test ( +- 1.84% ) 78896433101 instructions test # 0.17 insn per cycle ( +- 0.44% ) 10.0020430 +- 0.0000366 seconds time elapsed ( +- 0.00% ) 2) After applying this patchset: Performance counter stats for 'system wide' (5 runs): 841954709443 cycles test ( +- 15.80% ) (98.69%) 527258677936 instructions test # 0.63 insn per cycle ( +- 15.11% ) (98.68%) 10.01064 +- 0.00831 seconds time elapsed ( +- 0.08% ) We can see that IPC drops very seriously when calling down_read_trylock() at high frequency. After using SRCU, the IPC is at a normal level. Link: https://lkml.kernel.org/r/20230313112819.38938-4-zhengqi.arch@bytedance.comSigned-off-by: -
Qi Zheng authored
The shrinker_rwsem is a global read-write lock in shrinkers subsystem, which protects most operations such as slab shrink, registration and unregistration of shrinkers, etc. This can easily cause problems in the following cases. 1) When the memory pressure is high and there are many filesystems mounted or unmounted at the same time, slab shrink will be affected (down_read_trylock() failed). Such as the real workload mentioned by Kirill Tkhai: ``` One of the real workloads from my experience is start of an overcommitted node containing many starting containers after node crash (or many resuming containers after reboot for kernel update). In these cases memory pressure is huge, and the node goes round in long reclaim. ``` 2) If a shrinker is blocked (such as the case mentioned in [1]) and a writer comes in (such as mount a fs), then this writer will be blocked and cause all subsequent shrinker-related operations to be blocked. Even if there is no competitor when shrinking slab, there may still be a problem. If we have a long shrinker list and we do not reclaim enough memory with each shrinker, then the down_read_trylock() may be called with high frequency. Because of the poor multicore scalability of atomic operations, this can lead to a significant drop in IPC (instructions per cycle). So many times in history ([2],[3],[4],[5]), some people wanted to replace shrinker_rwsem trylock with SRCU in the slab shrink, but all these patches were abandoned because SRCU was not unconditionally enabled. But now, since commit 1cd0bd06093c ("rcu: Remove CONFIG_SRCU"), the SRCU is unconditionally enabled. So it's time to use SRCU to protect readers who previously held shrinker_rwsem. This commit uses SRCU to make global slab shrink lockless, the memcg slab shrink is handled in the subsequent patch. [1]. https://lore.kernel.org/lkml/20191129214541.3110-1-ptikhomirov@virtuozzo.com/ [2]. https://lore.kernel.org/all/1437080113.3596.2.camel@stgolabs.net/ [3]. https://lore.kernel.org/lkml/1510609063-3327-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp/ [4]. https://lore.kernel.org/lkml/153365347929.19074.12509495712735843805.stgit@localhost.localdomain/ [5]. https://lore.kernel.org/lkml/20210927074823.5825-1-sultan@kerneltoast.com/ Link: https://lkml.kernel.org/r/20230313112819.38938-3-zhengqi.arch@bytedance.comSigned-off-by: -
Qi Zheng authored
Patch series "make slab shrink lockless", v5. This patch series aims to make slab shrink lockless. 1. Background ============= On our servers, we often find the following system cpu hotspots: 52.22% [kernel] [k] down_read_trylock 19.60% [kernel] [k] up_read 8.86% [kernel] [k] shrink_slab 2.44% [kernel] [k] idr_find 1.25% [kernel] [k] count_shadow_nodes 1.18% [kernel] [k] shrink lruvec 0.71% [kernel] [k] mem_cgroup_iter 0.71% [kernel] [k] shrink_node 0.55% [kernel] [k] find_next_bit And we used bpftrace to capture its calltrace as follows: @[ down_read_trylock+1 shrink_slab+128 shrink_node+371 do_try_to_free_pages+232 try_to_free_pages+243 _alloc_pages_slowpath+771 _alloc_pages_nodemask+702 pagecache_get_page+255 filemap_fault+1361 ext4_filemap_fault+44 __do_fault+76 handle_mm_fault+3543 do_user_addr_fault+442 do_page_fault+48 page_fault+62 ]: 1161690 @[ down_read_trylock+1 shrink_slab+128 shrink_node+371 balance_pgdat+690 kswapd+389 kthread+246 ret_from_fork+31 ]: 8424884 @[ down_read_trylock+1 shrink_slab+128 shrink_node+371 do_try_to_free_pages+232 try_to_free_pages+243 __alloc_pages_slowpath+771 __alloc_pages_nodemask+702 __do_page_cache_readahead+244 filemap_fault+1674 ext4_filemap_fault+44 __do_fault+76 handle_mm_fault+3543 do_user_addr_fault+442 do_page_fault+48 page_fault+62 ]: 20917631 We can see that down_read_trylock() of shrinker_rwsem is being called with high frequency at that time. Because of the poor multicore scalability of atomic operations, this can lead to a significant drop in IPC (instructions per cycle). And more, the shrinker_rwsem is a global read-write lock in shrinkers subsystem, which protects most operations such as slab shrink, registration and unregistration of shrinkers, etc. This can easily cause problems in the following cases. 1) When the memory pressure is high and there are many filesystems mounted or unmounted at the same time, slab shrink will be affected (down_read_trylock() failed). Such as the real workload mentioned by Kirill Tkhai: ``` One of the real workloads from my experience is start of an overcommitted node containing many starting containers after node crash (or many resuming containers after reboot for kernel update). In these cases memory pressure is huge, and the node goes round in long reclaim. ``` 2) If a shrinker is blocked (such as the case mentioned in [1]) and a writer comes in (such as mount a fs), then this writer will be blocked and cause all subsequent shrinker-related operations to be blocked. [1]. https://lore.kernel.org/lkml/20191129214541.3110-1-ptikhomirov@virtuozzo.com/ All the above cases can be solved by replacing the shrinker_rwsem trylocks with SRCU. 2. Survey ========= Before doing the code implementation, I found that there were many similar submissions in the community: a. Davidlohr Bueso submitted a patch in 2015. Subject: [PATCH -next v2] mm: srcu-ify shrinkers Link: https://lore.kernel.org/all/1437080113.3596.2.camel@stgolabs.net/ Result: It was finally merged into the linux-next branch, but failed on arm allnoconfig (without CONFIG_SRCU) b. Tetsuo Handa submitted a patchset in 2017. Subject: [PATCH 1/2] mm,vmscan: Kill global shrinker lock. Link: https://lore.kernel.org/lkml/1510609063-3327-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp/ Result: Finally chose to use the current simple way (break when rwsem_is_contended()). And Christoph Hellwig suggested to using SRCU, but SRCU was not unconditionally enabled at the time. c. Kirill Tkhai submitted a patchset in 2018. Subject: [PATCH RFC 00/10] Introduce lockless shrink_slab() Link: https://lore.kernel.org/lkml/153365347929.19074.12509495712735843805.stgit@localhost.localdomain/ Result: At that time, SRCU was not unconditionally enabled, and there were some objections to enabling SRCU. Later, because Kirill's focus was moved to other things, this patchset was not continued to be updated. d. Sultan Alsawaf submitted a patch in 2021. Subject: [PATCH] mm: vmscan: Replace shrinker_rwsem trylocks with SRCU protection Link: https://lore.kernel.org/lkml/20210927074823.5825-1-sultan@kerneltoast.com/ Result: Rejected because SRCU was not unconditionally enabled. We can find that almost all these historical commits were abandoned because SRCU was not unconditionally enabled. But now SRCU has been unconditionally enable by Paul E. McKenney in 2023 [2], so it's time to replace shrinker_rwsem trylocks with SRCU. [2] https://lore.kernel.org/lkml/20230105003759.GA1769545@paulmck-ThinkPad-P17-Gen-1/ 3. Reproduction and testing =========================== We can reproduce the down_read_trylock() hotspot through the following script: ``` #!/bin/bash DIR="/root/shrinker/memcg/mnt" do_create() { mkdir -p /sys/fs/cgroup/memory/test mkdir -p /sys/fs/cgroup/perf_event/test echo 4G > /sys/fs/cgroup/memory/test/memory.limit_in_bytes for i in `seq 0 $1`; do mkdir -p /sys/fs/cgroup/memory/test/$i; echo $$ > /sys/fs/cgroup/memory/test/$i/cgroup.procs; echo $$ > /sys/fs/cgroup/perf_event/test/cgroup.procs; mkdir -p $DIR/$i; done } do_mount() { for i in `seq $1 $2`; do mount -t tmpfs $i $DIR/$i; done } do_touch() { for i in `seq $1 $2`; do echo $$ > /sys/fs/cgroup/memory/test/$i/cgroup.procs; echo $$ > /sys/fs/cgroup/perf_event/test/cgroup.procs; dd if=/dev/zero of=$DIR/$i/file$i bs=1M count=1 & done } case "$1" in touch) do_touch $2 $3 ;; test) do_create 4000 do_mount 0 4000 do_touch 0 3000 ;; *) exit 1 ;; esac ``` Save the above script, then run test and touch commands. Then we can use the following perf command to view hotspots: perf top -U -F 999 1) Before applying this patchset: 32.31% [kernel] [k] down_read_trylock 19.40% [kernel] [k] pv_native_safe_halt 16.24% [kernel] [k] up_read 15.70% [kernel] [k] shrink_slab 4.69% [kernel] [k] _find_next_bit 2.62% [kernel] [k] shrink_node 1.78% [kernel] [k] shrink_lruvec 0.76% [kernel] [k] do_shrink_slab 2) After applying this patchset: 27.83% [kernel] [k] _find_next_bit 16.97% [kernel] [k] shrink_slab 15.82% [kernel] [k] pv_native_safe_halt 9.58% [kernel] [k] shrink_node 8.31% [kernel] [k] shrink_lruvec 5.64% [kernel] [k] do_shrink_slab 3.88% [kernel] [k] mem_cgroup_iter At the same time, we use the following perf command to capture IPC information: perf stat -e cycles,instructions -G test -a --repeat 5 -- sleep 10 1) Before applying this patchset: Performance counter stats for 'system wide' (5 runs): 454187219766 cycles test ( +- 1.84% ) 78896433101 instructions test # 0.17 insn per cycle ( +- 0.44% ) 10.0020430 +- 0.0000366 seconds time elapsed ( +- 0.00% ) 2) After applying this patchset: Performance counter stats for 'system wide' (5 runs): 841954709443 cycles test ( +- 15.80% ) (98.69%) 527258677936 instructions test # 0.63 insn per cycle ( +- 15.11% ) (98.68%) 10.01064 +- 0.00831 seconds time elapsed ( +- 0.08% ) We can see that IPC drops very seriously when calling down_read_trylock() at high frequency. After using SRCU, the IPC is at a normal level. This patch (of 8): To prepare for the subsequent lockless memcg slab shrink, add a map_nr_max field to struct shrinker_info to records its own real shrinker_nr_max. Link: https://lkml.kernel.org/r/20230313112819.38938-1-zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/20230313112819.38938-2-zhengqi.arch@bytedance.comSigned-off-by: -
Lorenzo Stoakes authored
Update instances of alloc_pages(..., 0), __get_free_pages(..., 0) and __free_pages(..., 0) to use alloc_page(), __get_free_page() and __free_page() respectively in core code. Link: https://lkml.kernel.org/r/50c48ca4789f1da2a65795f2346f5ae3eff7d665.1678710232.git.lstoakes@gmail.comSigned-off-by:
Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by:
Mike Rapoport (IBM) <rppt@kernel.org> Acked-by:
Mel Gorman <mgorman@techsingularity.net> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christoph Hellwig <hch@infradead.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by:
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Peter Collingbourne authored
Code inspection reveals that PG_skip_kasan_poison is redundant with kasantag, because the former is intended to be set iff the latter is the match-all tag. It can also be observed that it's basically pointless to poison pages which have kasantag=0, because any pages with this tag would have been pointed to by pointers with match-all tags, so poisoning the pages would have little to no effect in terms of bug detection. Therefore, change the condition in should_skip_kasan_poison() to check kasantag instead, and remove PG_skip_kasan_poison and associated flags. Link: https://lkml.kernel.org/r/20230310042914.3805818-3-pcc@google.com Link: https://linux-review.googlesource.com/id/I57f825f2eaeaf7e8389d6cf4597c8a5821359838Signed-off-by:
Peter Collingbourne <pcc@google.com> Reviewed-by:
Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Will Deacon <will@kernel.org> Signed-off-by:
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Sebastian Andrzej Siewior authored
io_mapping_map_atomic_wc() disables preemption and pagefaults for historical reasons. The conversion to io_mapping_map_local_wc(), which only disables migration, cannot be done wholesale because quite some call sites need to be updated to accommodate with the changed semantics. On PREEMPT_RT enabled kernels the io_mapping_map_atomic_wc() semantics are problematic due to the implicit disabling of preemption which makes it impossible to acquire 'sleeping' spinlocks within the mapped atomic sections. PREEMPT_RT replaces the preempt_disable() with a migrate_disable() for more than a decade. It could be argued that this is a justification to do this unconditionally, but PREEMPT_RT covers only a limited number of architectures and it disables some functionality which limits the coverage further. Limit the replacement to PREEMPT_RT for now. This is also done kmap_atomic(). Link: https://lkml.kernel.org/r/20230310162905.O57Pj7hh@linutronix.deSigned-off-by:
Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reported-by:
Richard Weinberger <richard.weinberger@gmail.com> Link: https://lore.kernel.org/CAFLxGvw0WMxaMqYqJ5WgvVSbKHq2D2xcXTOgMCpgq9nDC-MWTQ@mail.gmail.com Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
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Luis Chamberlain authored
In doing experimentations with shmem having the option to avoid swap becomes a useful mechanism. One of the *raves* about brd over shmem is you can avoid swap, but that's not really a good reason to use brd if we can instead use shmem. Using brd has its own good reasons to exist, but just because "tmpfs" doesn't let you do that is not a great reason to avoid it if we can easily add support for it. I don't add support for reconfiguring incompatible options, but if we really wanted to we can add support for that. To avoid swap we use mapping_set_unevictable() upon inode creation, and put a WARN_ON_ONCE() stop-gap on writepages() for reclaim. Link: https://lkml.kernel.org/r/20230309230545.2930737-7-mcgrof@kernel.orgSigned-off-by:
Luis Chamberlain <mcgrof@kernel.org> Acked-by:
Christian Brauner <brauner@kernel.org> Tested-by:
Xin Hao <xhao@linux.alibaba.com> Reviewed-by:
Davidlohr Bueso <dave@stgolabs.net> Cc: Adam Manzanares <a.manzanares@samsung.com> Cc: David Hildenbrand <david@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Hugh Dickins <hughd@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Pankaj Raghav <p.raghav@samsung.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by:
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Luis Chamberlain authored
Update the docs to reflect a bit better why some folks prefer tmpfs over ramfs and clarify a bit more about the difference between brd ramdisks. While at it, add THP docs for tmpfs, both the mount options and the sysfs file. Link: https://lkml.kernel.org/r/20230309230545.2930737-6-mcgrof@kernel.orgSigned-off-by:
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Luis Chamberlain authored
In theory when info->flags & VM_LOCKED we should not be getting shem_writepage() called so we should be verifying this with a WARN_ON_ONCE(). Since we should not be swapping then best to ensure we also don't do the folio split earlier too. So just move the check early to avoid folio splits in case its a dubious call. We also have a similar early bail when !total_swap_pages so just move that earlier to avoid the possible folio split in the same situation. Link: https://lkml.kernel.org/r/20230309230545.2930737-5-mcgrof@kernel.orgSigned-off-by:
Yosry Ahmed <yosryahmed@google.com> Tested-by:
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Luis Chamberlain authored
i915_gem requires huge folios to be split when swapping. However we have check for usage of writepages() to ensure it used only for swap purposes later. Avoid the splits if we're not being called for reclaim, even if they should in theory not happen. This makes the conditions easier to follow on shem_writepage(). Link: https://lkml.kernel.org/r/20230309230545.2930737-4-mcgrof@kernel.orgSigned-off-by:
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Luis Chamberlain authored
shmem_writepage() sets up variables typically used *after* a possible huge page split. However even if that does happen the address space mapping should not change, and the inode does not change either. So it should be safe to set that from the very beginning. This commit makes no functional changes. Link: https://lkml.kernel.org/r/20230309230545.2930737-3-mcgrof@kernel.orgSigned-off-by:
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Luis Chamberlain authored
Patch series "tmpfs: add the option to disable swap", v2. I'm doing this work as part of future experimentation with tmpfs and the page cache, but given a common complaint found about tmpfs is the innability to work without the page cache I figured this might be useful to others. It turns out it is -- at least Christian Brauner indicates systemd uses ramfs for a few use-cases because they don't want to use swap and so having this option would let them move over to using tmpfs for those small use cases, see systemd-creds(1). To see if you hit swap: mkswap /dev/nvme2n1 swapon /dev/nvme2n1 free -h With swap - what we see today ============================= mount -t tmpfs -o size=5G tmpfs /data-tmpfs/ dd if=/dev/urandom of=/data-tmpfs/5g-rand2 bs=1G count=5 free -h total used free shared buff/cache available Mem: 3.7Gi 2.6Gi 1.2Gi 2.2Gi 2.2Gi 1.2Gi Swap: 99Gi 2.8Gi 97Gi Without swap ============= free -h total used free shared buff/cache available Mem: 3.7Gi 387Mi 3.4Gi 2.1Mi 57Mi 3.3Gi Swap: 99Gi 0B 99Gi mount -t tmpfs -o size=5G -o noswap tmpfs /data-tmpfs/ dd if=/dev/urandom of=/data-tmpfs/5g-rand2 bs=1G count=5 free -h total used free shared buff/cache available Mem: 3.7Gi 2.6Gi 1.2Gi 2.3Gi 2.3Gi 1.1Gi Swap: 99Gi 21Mi 99Gi The mix and match remount testing ================================= # Cannot disable swap after it was first enabled: mount -t tmpfs -o size=5G tmpfs /data-tmpfs/ mount -t tmpfs -o remount -o size=5G -o noswap tmpfs /data-tmpfs/ mount: /data-tmpfs: mount point not mounted or bad option. dmesg(1) may have more information after failed mount system call. dmesg -c tmpfs: Cannot disable swap on remount # Remount with the same noswap option is OK: mount -t tmpfs -o size=5G -o noswap tmpfs /data-tmpfs/ mount -t tmpfs -o remount -o size=5G -o noswap tmpfs /data-tmpfs/ dmesg -c # Trying to enable swap with a remount after it first disabled: mount -t tmpfs -o size=5G -o noswap tmpfs /data-tmpfs/ mount -t tmpfs -o remount -o size=5G tmpfs /data-tmpfs/ mount: /data-tmpfs: mount point not mounted or bad option. dmesg(1) may have more information after failed mount system call. dmesg -c tmpfs: Cannot enable swap on remount if it was disabled on first mount This patch (of 6): Matthew notes we should not need to check the folio lock on the writepage() callback so remove it. This sanity check has been lingering since linux-history days. We remove this as we tidy up the writepage() callback to make things a bit clearer. Link: https://lkml.kernel.org/r/20230309230545.2930737-1-mcgrof@kernel.org Link: https://lkml.kernel.org/r/20230309230545.2930737-2-mcgrof@kernel.orgSigned-off-by: -
Jingyu Wang authored
Link: https://lkml.kernel.org/r/20230309104813.170309-1-jingyuwang_vip@163.comSigned-off-by:
Jingyu Wang <jingyuwang_vip@163.com> Signed-off-by:
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Danilo Krummrich authored
Fix missing EXPORT_SYMBOL_GPL() statement for mas_preallocate(). It isn't actually used by anything yet, but mas_preallocate() is part of the maple tree's 'Advanced API'. All other functions of this API are exported already. Link: https://lkml.kernel.org/r/20230302011035.4928-1-dakr@redhat.comSigned-off-by:
Danilo Krummrich <dakr@redhat.com> Reviewed-by:
Liam R. Howlett <Liam.Howlett@oracle.com> Signed-off-by:
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