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* mm/zswap: don't return LRU_SKIP if we have dropped lru lockChengming Zhou2024-02-071-3/+1
| | | | | | | | | | | | | | | | | | | | | | 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>
* mm: zswap: fix objcg use-after-free in entry destructionJohannes Weiner2024-02-071-4/+4
| | | | | | | | | | | | | | 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>
* zswap: memcontrol: implement zswap writeback disablingNhat Pham2023-12-291-2/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mm: pass a folio to __swap_writepage()Matthew Wilcox (Oracle)2023-12-291-1/+1
| | | | | | | | | 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>
* mm: return the folio from __read_swap_cache_async()Matthew Wilcox (Oracle)2023-12-291-29/+29
| | | | | | | | | | | | | | | | | | | | 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>
* mm/zswap: change per-cpu mutex and buffer to per-acomp_ctxChengming Zhou2023-12-291-71/+33
| | | | | | | | | | | | | | | | | | | | | | | 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>
* mm/zswap: cleanup zswap_writeback_entry()Chengming Zhou2023-12-291-19/+10
| | | | | | | | | | | | | | | | | 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>
* mm/zswap: cleanup zswap_load()Chengming Zhou2023-12-291-9/+5
| | | | | | | | | | | | | | | | | 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>
* mm/zswap: refactor out __zswap_load()Chengming Zhou2023-12-291-60/+32
| | | | | | | | | | | | | | | | | | 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>
* mm/zswap: reuse dstmem when decompressChengming Zhou2023-12-291-32/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mm: memcg: restore subtree stats flushingYosry Ahmed2023-12-201-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* zswap: shrink zswap pool based on memory pressureNhat Pham2023-12-121-4/+188
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mm: memcg: add per-memcg zswap writeback statDomenico Cerasuolo2023-12-121-0/+4
| | | | | | | | | | | | | | | | | | | | | | | | | 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>
* zswap: make shrinking memcg-awareDomenico Cerasuolo2023-12-121-52/+216
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mm/zswap: replace kmap_atomic() with kmap_local_page()Fabio M. De Francesco2023-12-101-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* zswap: export compression failure statsNhat Pham2023-11-011-1/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mempolicy: alloc_pages_mpol() for NUMA policy without vmaHugh Dickins2023-10-251-2/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mm: zswap: fix pool refcount bug around shrink_worker()Johannes Weiner2023-10-181-2/+2
| | | | | | | | | | | | | | | | | | | | | 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>
* mm: zswap: fix potential memory corruption on duplicate storeDomenico Cerasuolo2023-09-291-0/+20
| | | | | | | | | | | | | | | | | | | | | 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>
* mm/swap: inline folio_set_swap_entry() and folio_swap_entry()David Hildenbrand2023-08-241-2/+2
| | | | | | | | | | | | | | | | | 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>
* mm: zswap: update comment for struct zswap_entryXiu Jianfeng2023-08-211-1/+2
| | | | | | | | | | | | 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>
* mm: zswap: kill zswap_get_swap_cache_page()Johannes Weiner2023-08-211-89/+53
| | | | | | | | | | | | | | | | 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>
* mm: zswap: tighten up entry invalidationJohannes Weiner2023-08-211-2/+2
| | | | | | | | | | | | | | | | | | | | 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>
* mm: zswap: use zswap_invalidate_entry() for duplicatesJohannes Weiner2023-08-211-3/+1
| | | | | | | | | | | | | | | | | | | | | | | | | 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>
* zswap: make zswap_load() take a folioMatthew Wilcox (Oracle)2023-08-211-4/+5
| | | | | | | | | | | | | | | | 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>
* memcg: convert get_obj_cgroup_from_page to get_obj_cgroup_from_folioMatthew Wilcox (Oracle)2023-08-211-1/+1
| | | | | | | | | | | | | | | 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>
* zswap: make zswap_store() take a folioMatthew Wilcox (Oracle)2023-08-211-6/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mm: kill frontswapJohannes Weiner2023-08-211-96/+63
| | | | | | | | | | | | | | | | | | | | | | 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>
* mm: zswap: multiple zpools supportYosry Ahmed2023-08-211-27/+54
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mm: zswap: fix double invalidate with exclusive loadsYosry Ahmed2023-06-231-9/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* Merge mm-hotfixes-stable into mm-stable to pick up depended-upon changes.Andrew Morton2023-06-231-2/+9
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| * zswap: do not shrink if cgroup may not zswapNhat Pham2023-06-121-2/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | mm: zswap: invaldiate entry after writebackDomenico Cerasuolo2023-06-191-16/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | mm: zswap: remove zswap_headerDomenico Cerasuolo2023-06-191-30/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | mm: zswap: simplify writeback functionDomenico Cerasuolo2023-06-191-51/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | mm: zswap: remove shrink from zpool interfaceDomenico Cerasuolo2023-06-191-20/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | mm: zswap: add pool shrinking mechanismDomenico Cerasuolo2023-06-191-5/+92
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | mm: zswap: support exclusive loadsYosry Ahmed2023-06-191-8/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | mm: zswap: shrink until can acceptDomenico Cerasuolo2023-06-091-3/+14
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* mm: fix zswap writeback race conditionDomenico Cerasuolo2023-05-171-0/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* Merge tag 'mm-stable-2023-04-27-15-30' of ↵Linus Torvalds2023-04-271-49/+89
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 ...
| * mm/zswap: delay the initialization of zswapLiu Shixin2023-04-181-17/+54
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * mm/zswap: replace zswap_init_{started/failed} with zswap_init_stateLiu Shixin2023-04-181-25/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * mm/zswap: remove zswap_entry_cache_{create,destroy} helper functionLiu Shixin2023-04-181-13/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * mm/zswap: try to avoid worst-case scenario on same element pagesTaejoon Song2023-03-281-4/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | zswap: remove MODULE_LICENSE in non-modulesNick Alcock2023-04-131-1/+0
|/ | | | | | | | | | | | | | | | | | | | | | | | | 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>
* zswap: fix writeback lock ordering for zsmallocJohannes Weiner2022-12-111-16/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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: do not allocate from atomic poolSergey Senozhatsky2022-11-301-2/+2
| | | | | | | | | | | | | | | | | | | 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>
* mm/swap: remove the end_write_func argument to __swap_writepageChristoph Hellwig2022-09-111-1/+1
| | | | | | | | | | | | 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>
* zswap: memcg accountingJohannes Weiner2022-05-191-7/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
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