kernel/linux.git/include/linux/list_lru.h, branch v6.19.11

list_lru: expand list_lru_add() docs with info about sublists

2025-01-14T06:40:38+00:00

The documentation for list_lru_add() and list_lru_del() has not been updated since lru lists were originally introduced by commit a38e40824844 ("list: add a new LRU list type"). Back then, list_lru stored all of the items in a single list, but the implementation has since been expanded to use many sublists internally. Thus, update the docs to mention that the requirements about not using the item with several lists at the same time also applies not using different sublists. Also mention that list_lru items are reparented when the memcg is deleted as discussed on the LKML [1]. Also fix incorrect use of 'Return value:' which should be 'Return:'. Link: https://lore.kernel.org/all/Z0eXrllVhRI9Ag5b@dread.disaster.area/ [1] Link: https://lkml.kernel.org/r/20241129-list_lru_memcg_docs-v2-1-e285ff1c481b@google.com Signed-off-by: Alice Ryhl Reviewed-by: Dave Chinner Acked-by: Muchun Song Reviewed-by: Nhat Pham Cc: Johannes Weiner Cc: Michal Hocko Cc: Qi Zheng Cc: Roman Gushchin Cc: Shakeel Butt Signed-off-by: Andrew Morton

mm/list_lru: simplify the list_lru walk callback function

2024-11-12T01:22:26+00:00

Now isolation no longer takes the list_lru global node lock, only use the per-cgroup lock instead. And this lock is inside the list_lru_one being walked, no longer needed to pass the lock explicitly. Link: https://lkml.kernel.org/r/20241104175257.60853-7-ryncsn@gmail.com Signed-off-by: Kairui Song Cc: Chengming Zhou Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Muchun Song Cc: Qi Zheng Cc: Roman Gushchin Cc: Shakeel Butt Cc: Waiman Long Signed-off-by: Andrew Morton

mm/list_lru: split the lock to per-cgroup scope

2024-11-12T01:22:26+00:00

Currently, every list_lru has a per-node lock that protects adding, deletion, isolation, and reparenting of all list_lru_one instances belonging to this list_lru on this node. This lock contention is heavy when multiple cgroups modify the same list_lru. This lock can be split into per-cgroup scope to reduce contention. To achieve this, we need a stable list_lru_one for every cgroup. This commit adds a lock to each list_lru_one and introduced a helper function lock_list_lru_of_memcg, making it possible to pin the list_lru of a memcg. Then reworked the reparenting process. Reparenting will switch the list_lru_one instances one by one. By locking each instance and marking it dead using the nr_items counter, reparenting ensures that all items in the corresponding cgroup (on-list or not, because items have a stable cgroup, see below) will see the list_lru_one switch synchronously. Objcg reparent is also moved after list_lru reparent so items will have a stable mem cgroup until all list_lru_one instances are drained. The only caller that doesn't work the *_obj interfaces are direct calls to list_lru_{add,del}. But it's only used by zswap and that's also based on objcg, so it's fine. This also changes the bahaviour of the isolation function when LRU_RETRY or LRU_REMOVED_RETRY is returned, because now releasing the lock could unblock reparenting and free the list_lru_one, isolation function will have to return withoug re-lock the lru. prepare() { mkdir /tmp/test-fs modprobe brd rd_nr=1 rd_size=33554432 mkfs.xfs -f /dev/ram0 mount -t xfs /dev/ram0 /tmp/test-fs for i in $(seq 1 512); do mkdir "/tmp/test-fs/$i" for j in $(seq 1 10240); do echo TEST-CONTENT > "/tmp/test-fs/$i/$j" done & done; wait } do_test() { read_worker() { sleep 1 tar -cv "$1" &>/dev/null } read_in_all() { cd "/tmp/test-fs" && ls for i in $(seq 1 512); do (exec sh -c 'echo "$PPID"') > "/sys/fs/cgroup/benchmark/$i/cgroup.procs" read_worker "$i" & done; wait } for i in $(seq 1 512); do mkdir -p "/sys/fs/cgroup/benchmark/$i" done echo +memory > /sys/fs/cgroup/benchmark/cgroup.subtree_control echo 512M > /sys/fs/cgroup/benchmark/memory.max echo 3 > /proc/sys/vm/drop_caches time read_in_all } Above script simulates compression of small files in multiple cgroups with memory pressure. Run prepare() then do_test for 6 times: Before: real 0m7.762s user 0m11.340s sys 3m11.224s real 0m8.123s user 0m11.548s sys 3m2.549s real 0m7.736s user 0m11.515s sys 3m11.171s real 0m8.539s user 0m11.508s sys 3m7.618s real 0m7.928s user 0m11.349s sys 3m13.063s real 0m8.105s user 0m11.128s sys 3m14.313s After this commit (about ~15% faster): real 0m6.953s user 0m11.327s sys 2m42.912s real 0m7.453s user 0m11.343s sys 2m51.942s real 0m6.916s user 0m11.269s sys 2m43.957s real 0m6.894s user 0m11.528s sys 2m45.346s real 0m6.911s user 0m11.095s sys 2m43.168s real 0m6.773s user 0m11.518s sys 2m40.774s Link: https://lkml.kernel.org/r/20241104175257.60853-6-ryncsn@gmail.com Signed-off-by: Kairui Song Cc: Chengming Zhou Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Muchun Song Cc: Qi Zheng Cc: Roman Gushchin Cc: Shakeel Butt Cc: Waiman Long Signed-off-by: Andrew Morton

mm/list_lru: don't pass unnecessary key parameters

2024-11-12T01:22:25+00:00

Patch series "mm/list_lru: Split list_lru lock into per-cgroup scope". When LOCKDEP is not enabled, lock_class_key is an empty struct that is never used. But the list_lru initialization function still takes a placeholder pointer as parameter, and the compiler cannot optimize it because the function is not static and exported. Remove this parameter and move it inside the list_lru struct. Only use it when LOCKDEP is enabled. Kernel builds with LOCKDEP will be slightly larger, while !LOCKDEP builds without it will be slightly smaller (the common case). Link: https://lkml.kernel.org/r/20241104175257.60853-1-ryncsn@gmail.com Link: https://lkml.kernel.org/r/20241104175257.60853-2-ryncsn@gmail.com Signed-off-by: Kairui Song Acked-by: Shakeel Butt Cc: Chengming Zhou Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Muchun Song Cc: Qi Zheng Cc: Roman Gushchin Cc: Waiman Long Signed-off-by: Andrew Morton

mm: remove CONFIG_MEMCG_KMEM

2024-07-10T19:14:54+00:00

CONFIG_MEMCG_KMEM used to be a user-visible option for whether slab tracking is enabled. It has been default-enabled and equivalent to CONFIG_MEMCG for almost a decade. We've only grown more kernel memory accounting sites since, and there is no imaginable cgroup usecase going forward that wants to track user pages but not the multitude of user-drivable kernel allocations. Link: https://lkml.kernel.org/r/20240701153148.452230-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Roman Gushchin Acked-by: Michal Hocko Acked-by: Shakeel Butt Acked-by: David Hildenbrand Cc: Muchun Song Signed-off-by: Andrew Morton

mm/zswap: stop lru list shrinking when encounter warm region

2024-02-22T18:24:54+00:00

When the shrinker encounter an existing folio in swap cache, it means we are shrinking into the warmer region. We should terminate shrinking if we're in the dynamic shrinker context. This patch add LRU_STOP to support this, to avoid overshrinking. Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-3-99d4084260a0@bytedance.com Signed-off-by: Chengming Zhou Acked-by: Johannes Weiner Acked-by: Nhat Pham Reviewed-by: Yosry Ahmed Signed-off-by: Andrew Morton

mm/list_lru: remove list_lru_putback()

2024-02-22T18:24:42+00:00

Since the only user zswap_lru_putback() has gone, remove list_lru_putback() too. Link: https://lkml.kernel.org/r/20240126-zswap-writeback-race-v2-3-b10479847099@bytedance.com Signed-off-by: Chengming Zhou Acked-by: Yosry Ahmed Cc: Chris Li Cc: Johannes Weiner Cc: Nhat Pham Signed-off-by: Andrew Morton

mm: list_lru: remove unused macro list_lru_init_key()

2024-02-22T00:00:02+00:00

list_lru_init_key() isn't used by anyone, remove it to clean up. Link: https://lkml.kernel.org/r/20231228062715.338672-2-haifeng.xu@shopee.com Signed-off-by: Haifeng Xu Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Michal Hocko Cc: Shakeel Butt Signed-off-by: Andrew Morton

list_lru: allow explicit memcg and NUMA node selection

2023-12-12T18:57:01+00:00

Patch series "workload-specific and memory pressure-driven zswap writeback", v8. There are currently several issues with zswap writeback: 1. There is only a single global LRU for zswap, making it impossible to perform worload-specific shrinking - an memcg under memory pressure 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 But this solution leaves a lot to be desired, as we still do not have an avenue for an memcg to free up its own memory locked up in the zswap pool. 2. 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 series solves these issues by separating the global zswap LRU into per-memcg and per-NUMA LRUs, and performs workload-specific (i.e memcg- and NUMA-aware) zswap writeback under memory pressure. The new 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. 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. This patch (of 6): The interface of list_lru is based on the assumption that the list node and the data it represents belong to the same allocated on the correct node/memcg. While this assumption is valid for existing slab objects LRU such as dentries and inodes, it is undocumented, and rather inflexible for certain potential list_lru users (such as the upcoming zswap shrinker and the THP shrinker). It has caused us a lot of issues during our development. This patch changes list_lru interface so that the caller must explicitly specify numa node and memcg when adding and removing objects. The old list_lru_add() and list_lru_del() are renamed to list_lru_add_obj() and list_lru_del_obj(), respectively. It also extends the list_lru API with a new function, list_lru_putback, which undoes a previous list_lru_isolate call. Unlike list_lru_add, it does not increment the LRU node count (as list_lru_isolate does not decrement the node count). list_lru_putback also allows for explicit memcg and NUMA node selection. Link: https://lkml.kernel.org/r/20231130194023.4102148-1-nphamcs@gmail.com Link: https://lkml.kernel.org/r/20231130194023.4102148-2-nphamcs@gmail.com Signed-off-by: Nhat Pham Suggested-by: Johannes Weiner Acked-by: Johannes Weiner Tested-by: Bagas Sanjaya Cc: Chris Li Cc: Dan Streetman Cc: Domenico Cerasuolo Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Seth Jennings Cc: Shakeel Butt Cc: Shuah Khan Cc: Vitaly Wool Cc: Yosry Ahmed Signed-off-by: Andrew Morton

mm: list_lru: Update kernel documentation to follow the requirements

2023-12-11T00:51:52+00:00

kernel-doc is not happy about documentation in list_lru.h: list_lru.h:90: warning: Function parameter or member 'lru' not described in 'list_lru_add' list_lru.h:90: warning: Excess function parameter 'list_lru' description in 'list_lru_add' list_lru.h:90: warning: No description found for return value of 'list_lru_add' list_lru.h:103: warning: Function parameter or member 'lru' not described in 'list_lru_del' list_lru.h:103: warning: Excess function parameter 'list_lru' description in 'list_lru_del' list_lru.h:103: warning: No description found for return value of 'list_lru_del' list_lru.h:116: warning: No description found for return value of 'list_lru_count_one' list_lru.h:168: warning: No description found for return value of 'list_lru_walk_one' list_lru.h:185: warning: No description found for return value of 'list_lru_walk_one_irq' Fix the documentation accordingly. While at it, fix the references to the parameters in functions inside the long descriptions, on which the above script is not complaining (yet?). Link: https://lkml.kernel.org/r/20231123172320.2434780-1-andriy.shevchenko@linux.intel.com Signed-off-by: Andy Shevchenko Cc: Rasmus Villemoes Signed-off-by: Andrew Morton