kernel/linux.git/include/linux/memcontrol.h, branch v6.12.80

mm: count zeromap read and set for swapout and swapin

2024-11-11T08:00:37+00:00

When the proportion of folios from the zeromap is small, missing their accounting may not significantly impact profiling. However, it's easy to construct a scenario where this becomes an issue—for example, allocating 1 GB of memory, writing zeros from userspace, followed by MADV_PAGEOUT, and then swapping it back in. In this case, the swap-out and swap-in counts seem to vanish into a black hole, potentially causing semantic ambiguity. On the other hand, Usama reported that zero-filled pages can exceed 10% in workloads utilizing zswap, while Hailong noted that some app in Android have more than 6% zero-filled pages. Before commit 0ca0c24e3211 ("mm: store zero pages to be swapped out in a bitmap"), both zswap and zRAM implemented similar optimizations, leading to these optimized-out pages being counted in either zswap or zRAM counters (with pswpin/pswpout also increasing for zRAM). With zeromap functioning prior to both zswap and zRAM, userspace will no longer detect these swap-out and swap-in actions. We have three ways to address this: 1. Introduce a dedicated counter specifically for the zeromap. 2. Use pswpin/pswpout accounting, treating the zero map as a standard backend. This approach aligns with zRAM's current handling of same-page fills at the device level. However, it would mean losing the optimized-out page counters previously available in zRAM and would not align with systems using zswap. Additionally, as noted by Nhat Pham, pswpin/pswpout counters apply only to I/O done directly to the backend device. 3. Count zeromap pages under zswap, aligning with system behavior when zswap is enabled. However, this would not be consistent with zRAM, nor would it align with systems lacking both zswap and zRAM. Given the complications with options 2 and 3, this patch selects option 1. We can find these counters from /proc/vmstat (counters for the whole system) and memcg's memory.stat (counters for the interested memcg). For example: $ grep -E 'swpin_zero|swpout_zero' /proc/vmstat swpin_zero 1648 swpout_zero 33536 $ grep -E 'swpin_zero|swpout_zero' /sys/fs/cgroup/system.slice/memory.stat swpin_zero 3905 swpout_zero 3985 This patch does not address any specific zeromap bug, but the missing swpout and swpin counts for zero-filled pages can be highly confusing and may mislead user-space agents that rely on changes in these counters as indicators. Therefore, we add a Fixes tag to encourage the inclusion of this counter in any kernel versions with zeromap. Many thanks to Kanchana for the contribution of changing count_objcg_event() to count_objcg_events() to support large folios[1], which has now been incorporated into this patch. [1] https://lkml.kernel.org/r/20241001053222.6944-5-kanchana.p.sridhar@intel.com Link: https://lkml.kernel.org/r/20241107011246.59137-1-21cnbao@gmail.com Fixes: 0ca0c24e3211 ("mm: store zero pages to be swapped out in a bitmap") Co-developed-by: Kanchana P Sridhar Signed-off-by: Barry Song Reviewed-by: Nhat Pham Reviewed-by: Chengming Zhou Acked-by: Johannes Weiner Cc: Usama Arif Cc: Yosry Ahmed Cc: Hailong Liu Cc: David Hildenbrand Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Cc: Shakeel Butt Cc: Andi Kleen Cc: Baolin Wang Cc: Chris Li Cc: "Huang, Ying" Cc: Kairui Song Cc: Ryan Roberts Signed-off-by: Andrew Morton

mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios

2024-09-17T08:07:01+00:00

With large folios swap-in, we might need to uncharge multiple entries all together, add nr argument in mem_cgroup_swapin_uncharge_swap(). For the existing two users, just pass nr=1. Link: https://lkml.kernel.org/r/20240908232119.2157-3-21cnbao@gmail.com Signed-off-by: Barry Song Acked-by: Chris Li Reviewed-by: Yosry Ahmed Cc: Shakeel Butt Cc: Baolin Wang Cc: Christoph Hellwig Cc: David Hildenbrand Cc: Gao Xiang Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Johannes Weiner Cc: Kairui Song Cc: Kairui Song Cc: Kalesh Singh Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Minchan Kim Cc: Nhat Pham Cc: Ryan Roberts Cc: Sergey Senozhatsky Cc: Suren Baghdasaryan Cc: Yang Shi Cc: Chuanhua Han Cc: Kanchana P Sridhar Cc: Usama Arif Signed-off-by: Andrew Morton

mm: restart if multiple traversals raced

2024-09-09T23:39:16+00:00

Currently, if multiple reclaimers raced on the same position, the reclaimers which detect the race will still reclaim from the same memcg. Instead, the reclaimers which detect the race should move on to the next memcg in the hierarchy. So, in the case where multiple traversals race, jump back to the start of the mem_cgroup_iter() function to find the next memcg in the hierarchy to reclaim from. Link: https://lkml.kernel.org/r/20240905003058.1859929-5-kinseyho@google.com Reported-by: syzbot+e099d407346c45275ce9@syzkaller.appspotmail.com Closes: https://lore.kernel.org/000000000000817cf10620e20d33@google.com/ Signed-off-by: Kinsey Ho Reviewed-by: T.J. Mercier Cc: Johannes Weiner Cc: Michal Hocko Cc: Michal Koutný Cc: Muchun Song Cc: Roman Gushchin Cc: Shakeel Butt Cc: Tejun Heo Cc: Yosry Ahmed Cc: Zefan Li Cc: Hugh Dickins Signed-off-by: Andrew Morton

mm,memcg: provide per-cgroup counters for NUMA balancing operations

2024-09-04T04:15:36+00:00

The ability to observe the demotion and promotion decisions made by the kernel on a per-cgroup basis is important for monitoring and tuning containerized workloads on machines equipped with tiered memory. Different containers in the system may experience drastically different memory tiering actions that cannot be distinguished from the global counters alone. For example, a container running a workload that has a much hotter memory accesses will likely see more promotions and fewer demotions, potentially depriving a colocated container of top tier memory to such an extent that its performance degrades unacceptably. For another example, some containers may exhibit longer periods between data reuse, causing much more numa_hint_faults than numa_pages_migrated. In this case, tuning hot_threshold_ms may be appropriate, but the signal can easily be lost if only global counters are available. In the long term, we hope to introduce per-cgroup control of promotion and demotion actions to implement memory placement policies in tiering. This patch set adds seven counters to memory.stat in a cgroup: numa_pages_migrated, numa_pte_updates, numa_hint_faults, pgdemote_kswapd, pgdemote_khugepaged, pgdemote_direct and pgpromote_success. pgdemote_* and pgpromote_success are also available in memory.numa_stat. count_memcg_events_mm() is added to count multiple event occurrences at once, and get_mem_cgroup_from_folio() is added because we need to get a reference to the memcg of a folio before it's migrated to track numa_pages_migrated. The accounting of PGDEMOTE_* is moved to shrink_inactive_list() before being changed to per-cgroup. [kaiyang2@cs.cmu.edu: add documentation of the memcg counters in cgroup-v2.rst] Link: https://lkml.kernel.org/r/20240814235122.252309-1-kaiyang2@cs.cmu.edu Link: https://lkml.kernel.org/r/20240814174227.30639-1-kaiyang2@cs.cmu.edu Signed-off-by: Kaiyang Zhao Cc: David Rientjes Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Shakeel Butt Cc: Wei Xu Signed-off-by: Andrew Morton

memcg: allocate v1 event percpu only on v1 deployment

2024-09-02T03:26:20+00:00

Currently memcg->events_percpu gets allocated on v2 deployments. Let's move the allocation to v1 only codebase. This is not needed in v2. Link: https://lkml.kernel.org/r/20240815050453.1298138-7-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: T.J. Mercier Signed-off-by: Andrew Morton

memcg: move v1 only percpu stats in separate struct

2024-09-02T03:26:18+00:00

Patch series "memcg: further decouple v1 code from v2". Some of the v1 code is still in v2 code base due to v1 fields in the struct memcg_vmstats_percpu. This field decouples those fileds from v2 struct and move all the related code into v1 only code base. This patch (of 7): At the moment struct memcg_vmstats_percpu contains two v1 only fields which consumes memory even when CONFIG_MEMCG_V1 is not enabled. In addition there are v1 only functions accessing them and are in the main memcontrol source file and can not be moved to v1 only source file due to these fields. Let's move these fields into their own struct. Later patches will move the functions accessing them to v1 source file and only allocate these fields when CONFIG_MEMCG_V1 is enabled. Link: https://lkml.kernel.org/r/20240815050453.1298138-1-shakeel.butt@linux.dev Link: https://lkml.kernel.org/r/20240815050453.1298138-2-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: T.J. Mercier Signed-off-by: Andrew Morton

mm: kmem: add lockdep assertion to obj_cgroup_memcg

2024-09-02T03:26:14+00:00

obj_cgroup_memcg() is supposed to safe to prevent the returned memory cgroup from being freed only when the caller is holding the rcu read lock or objcg_lock or cgroup_mutex. It is very easy to ignore thoes conditions when users call some upper APIs which call obj_cgroup_memcg() internally like mem_cgroup_from_slab_obj() (See the link below). So it is better to add lockdep assertion to obj_cgroup_memcg() to find those issues ASAP. Because there is no user of obj_cgroup_memcg() holding objcg_lock to make the returned memory cgroup safe, do not add objcg_lock assertion (We should export objcg_lock if we really want to do). Additionally, this is some internal implementation detail of memcg and should not be accessible outside memcg code. Some users like __mem_cgroup_uncharge() do not care the lifetime of the returned memory cgroup, which just want to know if the folio is charged to a memory cgroup, therefore, they do not need to hold the needed locks. In which case, introduce a new helper folio_memcg_charged() to do this. Compare it to folio_memcg(), it could eliminate a memory access of objcg->memcg for kmem, actually, a really small gain. [songmuchun@bytedance.com: fix split_page_memcg()] Link: https://lkml.kernel.org/r/20240819080415.44964-1-songmuchun@bytedance.com Link: https://lore.kernel.org/all/20240718083607.42068-1-songmuchun@bytedance.com/ Link: https://lkml.kernel.org/r/20240814093415.17634-1-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Shakeel Butt Acked-by: Roman Gushchin Acked-by: Vlastimil Babka Cc: Johannes Weiner Cc: Michal Hocko Signed-off-by: Andrew Morton

mm, memcg: cg2 memory{.swap,}.peak write handlers

2024-09-02T03:25:53+00:00

Patch series "mm, memcg: cg2 memory{.swap,}.peak write handlers", v7. This patch (of 2): Other mechanisms for querying the peak memory usage of either a process or v1 memory cgroup allow for resetting the high watermark. Restore parity with those mechanisms, but with a less racy API. For example: - Any write to memory.max_usage_in_bytes in a cgroup v1 mount resets the high watermark. - writing "5" to the clear_refs pseudo-file in a processes's proc directory resets the peak RSS. This change is an evolution of a previous patch, which mostly copied the cgroup v1 behavior, however, there were concerns about races/ownership issues with a global reset, so instead this change makes the reset filedescriptor-local. Writing any non-empty string to the memory.peak and memory.swap.peak pseudo-files reset the high watermark to the current usage for subsequent reads through that same FD. Notably, following Johannes's suggestion, this implementation moves the O(FDs that have written) behavior onto the FD write(2) path. Instead, on the page-allocation path, we simply add one additional watermark to conditionally bump per-hierarchy level in the page-counter. Additionally, this takes Longman's suggestion of nesting the page-charging-path checks for the two watermarks to reduce the number of common-case comparisons. This behavior is particularly useful for work scheduling systems that need to track memory usage of worker processes/cgroups per-work-item. Since memory can't be squeezed like CPU can (the OOM-killer has opinions), these systems need to track the peak memory usage to compute system/container fullness when binpacking workitems. Most notably, Vimeo's use-case involves a system that's doing global binpacking across many Kubernetes pods/containers, and while we can use PSI for some local decisions about overload, we strive to avoid packing workloads too tightly in the first place. To facilitate this, we track the peak memory usage. However, since we run with long-lived workers (to amortize startup costs) we need a way to track the high watermark while a work-item is executing. Polling runs the risk of missing short spikes that last for timescales below the polling interval, and peak memory tracking at the cgroup level is otherwise perfect for this use-case. As this data is used to ensure that binpacked work ends up with sufficient headroom, this use-case mostly avoids the inaccuracies surrounding reclaimable memory. Link: https://lkml.kernel.org/r/20240730231304.761942-1-davidf@vimeo.com Link: https://lkml.kernel.org/r/20240729143743.34236-1-davidf@vimeo.com Link: https://lkml.kernel.org/r/20240729143743.34236-2-davidf@vimeo.com Signed-off-by: David Finkel Suggested-by: Johannes Weiner Suggested-by: Waiman Long Acked-by: Johannes Weiner Reviewed-by: Michal Koutný Acked-by: Tejun Heo Reviewed-by: Roman Gushchin Cc: Jonathan Corbet Cc: Michal Hocko Cc: Muchun Song Cc: Shakeel Butt Cc: Shuah Khan Cc: Zefan Li Signed-off-by: Andrew Morton

mm: kmem: remove mem_cgroup_from_obj()

2024-09-02T03:25:46+00:00

There is no user of mem_cgroup_from_obj(), remove it. Link: https://lkml.kernel.org/r/20240718091821.44740-1-songmuchun@bytedance.com Signed-off-by: Muchun Song Acked-by: Shakeel Butt Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Michal Hocko Signed-off-by: Andrew Morton

mm: memcg: add cacheline padding after lruvec in mem_cgroup_per_node

2024-07-26T21:33:09+00:00

Oliver Sand reported a performance regression caused by commit 98c9daf5ae6b ("mm: memcg: guard memcg1-specific members of struct mem_cgroup_per_node"), which puts some fields of the mem_cgroup_per_node structure under the CONFIG_MEMCG_V1 config option. Apparently it causes a false cache sharing between lruvec and lru_zone_size members of the structure. Fix it by adding an explicit padding after the lruvec member. Even though the padding is not required with CONFIG_MEMCG_V1 set, it seems like the introduced memory overhead is not significant enough to warrant another divergence in the mem_cgroup_per_node layout, so the padding is added unconditionally. Link: https://lkml.kernel.org/r/20240723171244.747521-1-roman.gushchin@linux.dev Fixes: 98c9daf5ae6b ("mm: memcg: guard memcg1-specific members of struct mem_cgroup_per_node") Signed-off-by: Roman Gushchin Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202407121335.31a10cb6-oliver.sang@intel.com Tested-by: Oliver Sang Acked-by: Shakeel Butt Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Signed-off-by: Andrew Morton