kernel/linux.git/mm/memcontrol.c, branch v6.12.80

memcg: always call cond_resched() after fn()

2025-05-29T09:03:22+00:00

commit 06717a7b6c86514dbd6ab322e8083ffaa4db5712 upstream. I am seeing soft lockup on certain machine types when a cgroup OOMs. This is happening because killing the process in certain machine might be very slow, which causes the soft lockup and RCU stalls. This happens usually when the cgroup has MANY processes and memory.oom.group is set. Example I am seeing in real production: [462012.244552] Memory cgroup out of memory: Killed process 3370438 (crosvm) .... .... [462037.318059] Memory cgroup out of memory: Killed process 4171372 (adb) .... [462037.348314] watchdog: BUG: soft lockup - CPU#64 stuck for 26s! [stat_manager-ag:1618982] .... Quick look at why this is so slow, it seems to be related to serial flush for certain machine types. For all the crashes I saw, the target CPU was at console_flush_all(). In the case above, there are thousands of processes in the cgroup, and it is soft locking up before it reaches the 1024 limit in the code (which would call the cond_resched()). So, cond_resched() in 1024 blocks is not sufficient. Remove the counter-based conditional rescheduling logic and call cond_resched() unconditionally after each task iteration, after fn() is called. This avoids the lockup independently of how slow fn() is. Link: https://lkml.kernel.org/r/20250523-memcg_fix-v1-1-ad3eafb60477@debian.org Fixes: ade81479c7dd ("memcg: fix soft lockup in the OOM process") Signed-off-by: Breno Leitao Suggested-by: Rik van Riel Acked-by: Shakeel Butt Cc: Michael van der Westhuizen Cc: Usama Arif Cc: Pavel Begunkov Cc: Chen Ridong Cc: Greg Kroah-Hartman Cc: Johannes Weiner Cc: Michal Hocko Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

memcg: drain obj stock on cpu hotplug teardown

2025-03-28T21:03:30+00:00

commit 9f01b4954490d4ccdbcc2b9be34a9921ceee9cbb upstream. Currently on cpu hotplug teardown, only memcg stock is drained but we need to drain the obj stock as well otherwise we will miss the stats accumulated on the target cpu as well as the nr_bytes cached. The stats include MEMCG_KMEM, NR_SLAB_RECLAIMABLE_B & NR_SLAB_UNRECLAIMABLE_B. In addition we are leaking reference to struct obj_cgroup object. Link: https://lkml.kernel.org/r/20250310230934.2913113-1-shakeel.butt@linux.dev Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") Signed-off-by: Shakeel Butt Reviewed-by: Roman Gushchin Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

memcg: fix soft lockup in the OOM process

2025-02-08T08:58:19+00:00

commit ade81479c7dda1ce3eedb215c78bc615bbd04f06 upstream. A soft lockup issue was found in the product with about 56,000 tasks were in the OOM cgroup, it was traversing them when the soft lockup was triggered. watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [VM Thread:1503066] CPU: 2 PID: 1503066 Comm: VM Thread Kdump: loaded Tainted: G Hardware name: Huawei Cloud OpenStack Nova, BIOS RIP: 0010:console_unlock+0x343/0x540 RSP: 0000:ffffb751447db9a0 EFLAGS: 00000247 ORIG_RAX: ffffffffffffff13 RAX: 0000000000000001 RBX: 0000000000000000 RCX: 00000000ffffffff RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000247 RBP: ffffffffafc71f90 R08: 0000000000000000 R09: 0000000000000040 R10: 0000000000000080 R11: 0000000000000000 R12: ffffffffafc74bd0 R13: ffffffffaf60a220 R14: 0000000000000247 R15: 0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2fe6ad91f0 CR3: 00000004b2076003 CR4: 0000000000360ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: vprintk_emit+0x193/0x280 printk+0x52/0x6e dump_task+0x114/0x130 mem_cgroup_scan_tasks+0x76/0x100 dump_header+0x1fe/0x210 oom_kill_process+0xd1/0x100 out_of_memory+0x125/0x570 mem_cgroup_out_of_memory+0xb5/0xd0 try_charge+0x720/0x770 mem_cgroup_try_charge+0x86/0x180 mem_cgroup_try_charge_delay+0x1c/0x40 do_anonymous_page+0xb5/0x390 handle_mm_fault+0xc4/0x1f0 This is because thousands of processes are in the OOM cgroup, it takes a long time to traverse all of them. As a result, this lead to soft lockup in the OOM process. To fix this issue, call 'cond_resched' in the 'mem_cgroup_scan_tasks' function per 1000 iterations. For global OOM, call 'touch_softlockup_watchdog' per 1000 iterations to avoid this issue. Link: https://lkml.kernel.org/r/20241224025238.3768787-1-chenridong@huaweicloud.com Fixes: 9cbb78bb3143 ("mm, memcg: introduce own oom handler to iterate only over its own threads") Signed-off-by: Chen Ridong Acked-by: Michal Hocko Cc: Roman Gushchin Cc: Johannes Weiner Cc: Shakeel Butt Cc: Muchun Song Cc: Michal Koutný Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

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/thp: fix deferred split unqueue naming and locking

2024-11-06T00:49:54+00:00

Recent changes are putting more pressure on THP deferred split queues: under load revealing long-standing races, causing list_del corruptions, "Bad page state"s and worse (I keep BUGs in both of those, so usually don't get to see how badly they end up without). The relevant recent changes being 6.8's mTHP, 6.10's mTHP swapout, and 6.12's mTHP swapin, improved swap allocation, and underused THP splitting. Before fixing locking: rename misleading folio_undo_large_rmappable(), which does not undo large_rmappable, to folio_unqueue_deferred_split(), which is what it does. But that and its out-of-line __callee are mm internals of very limited usability: add comment and WARN_ON_ONCEs to check usage; and return a bool to say if a deferred split was unqueued, which can then be used in WARN_ON_ONCEs around safety checks (sparing callers the arcane conditionals in __folio_unqueue_deferred_split()). Just omit the folio_unqueue_deferred_split() from free_unref_folios(), all of whose callers now call it beforehand (and if any forget then bad_page() will tell) - except for its caller put_pages_list(), which itself no longer has any callers (and will be deleted separately). Swapout: mem_cgroup_swapout() has been resetting folio->memcg_data 0 without checking and unqueueing a THP folio from deferred split list; which is unfortunate, since the split_queue_lock depends on the memcg (when memcg is enabled); so swapout has been unqueueing such THPs later, when freeing the folio, using the pgdat's lock instead: potentially corrupting the memcg's list. __remove_mapping() has frozen refcount to 0 here, so no problem with calling folio_unqueue_deferred_split() before resetting memcg_data. That goes back to 5.4 commit 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware"): which included a check on swapcache before adding to deferred queue, but no check on deferred queue before adding THP to swapcache. That worked fine with the usual sequence of events in reclaim (though there were a couple of rare ways in which a THP on deferred queue could have been swapped out), but 6.12 commit dafff3f4c850 ("mm: split underused THPs") avoids splitting underused THPs in reclaim, which makes swapcache THPs on deferred queue commonplace. Keep the check on swapcache before adding to deferred queue? Yes: it is no longer essential, but preserves the existing behaviour, and is likely to be a worthwhile optimization (vmstat showed much more traffic on the queue under swapping load if the check was removed); update its comment. Memcg-v1 move (deprecated): mem_cgroup_move_account() has been changing folio->memcg_data without checking and unqueueing a THP folio from the deferred list, sometimes corrupting "from" memcg's list, like swapout. Refcount is non-zero here, so folio_unqueue_deferred_split() can only be used in a WARN_ON_ONCE to validate the fix, which must be done earlier: mem_cgroup_move_charge_pte_range() first try to split the THP (splitting of course unqueues), or skip it if that fails. Not ideal, but moving charge has been requested, and khugepaged should repair the THP later: nobody wants new custom unqueueing code just for this deprecated case. The 87eaceb3faa5 commit did have the code to move from one deferred list to another (but was not conscious of its unsafety while refcount non-0); but that was removed by 5.6 commit fac0516b5534 ("mm: thp: don't need care deferred split queue in memcg charge move path"), which argued that the existence of a PMD mapping guarantees that the THP cannot be on a deferred list. As above, false in rare cases, and now commonly false. Backport to 6.11 should be straightforward. Earlier backports must take care that other _deferred_list fixes and dependencies are included. There is not a strong case for backports, but they can fix cornercases. Link: https://lkml.kernel.org/r/8dc111ae-f6db-2da7-b25c-7a20b1effe3b@google.com Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware") Fixes: dafff3f4c850 ("mm: split underused THPs") Signed-off-by: Hugh Dickins Acked-by: David Hildenbrand Reviewed-by: Yang Shi Cc: Baolin Wang Cc: Barry Song Cc: Chris Li Cc: Johannes Weiner Cc: Kefeng Wang Cc: Kirill A. Shutemov Cc: Matthew Wilcox (Oracle) Cc: Nhat Pham Cc: Ryan Roberts Cc: Shakeel Butt Cc: Usama Arif Cc: Wei Yang Cc: Zi Yan Cc: Signed-off-by: Andrew Morton

mm/thp: fix deferred split queue not partially_mapped

2024-11-06T00:49:54+00:00

Merge tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-09-21T14:29:05+00:00

Pull MM updates from Andrew Morton: "Along with the usual shower of singleton patches, notable patch series in this pull request are: - "Align kvrealloc() with krealloc()" from Danilo Krummrich. Adds consistency to the APIs and behaviour of these two core allocation functions. This also simplifies/enables Rustification. - "Some cleanups for shmem" from Baolin Wang. No functional changes - mode code reuse, better function naming, logic simplifications. - "mm: some small page fault cleanups" from Josef Bacik. No functional changes - code cleanups only. - "Various memory tiering fixes" from Zi Yan. A small fix and a little cleanup. - "mm/swap: remove boilerplate" from Yu Zhao. Code cleanups and simplifications and .text shrinkage. - "Kernel stack usage histogram" from Pasha Tatashin and Shakeel Butt. This is a feature, it adds new feilds to /proc/vmstat such as $ grep kstack /proc/vmstat kstack_1k 3 kstack_2k 188 kstack_4k 11391 kstack_8k 243 kstack_16k 0 which tells us that 11391 processes used 4k of stack while none at all used 16k. Useful for some system tuning things, but partivularly useful for "the dynamic kernel stack project". - "kmemleak: support for percpu memory leak detect" from Pavel Tikhomirov. Teaches kmemleak to detect leaksage of percpu memory. - "mm: memcg: page counters optimizations" from Roman Gushchin. "3 independent small optimizations of page counters". - "mm: split PTE/PMD PT table Kconfig cleanups+clarifications" from David Hildenbrand. Improves PTE/PMD splitlock detection, makes powerpc/8xx work correctly by design rather than by accident. - "mm: remove arch_make_page_accessible()" from David Hildenbrand. Some folio conversions which make arch_make_page_accessible() unneeded. - "mm, memcg: cg2 memory{.swap,}.peak write handlers" fro David Finkel. Cleans up and fixes our handling of the resetting of the cgroup/process peak-memory-use detector. - "Make core VMA operations internal and testable" from Lorenzo Stoakes. Rationalizaion and encapsulation of the VMA manipulation APIs. With a view to better enable testing of the VMA functions, even from a userspace-only harness. - "mm: zswap: fixes for global shrinker" from Takero Funaki. Fix issues in the zswap global shrinker, resulting in improved performance. - "mm: print the promo watermark in zoneinfo" from Kaiyang Zhao. Fill in some missing info in /proc/zoneinfo. - "mm: replace follow_page() by folio_walk" from David Hildenbrand. Code cleanups and rationalizations (conversion to folio_walk()) resulting in the removal of follow_page(). - "improving dynamic zswap shrinker protection scheme" from Nhat Pham. Some tuning to improve zswap's dynamic shrinker. Significant reductions in swapin and improvements in performance are shown. - "mm: Fix several issues with unaccepted memory" from Kirill Shutemov. Improvements to the new unaccepted memory feature, - "mm/mprotect: Fix dax puds" from Peter Xu. Implements mprotect on DAX PUDs. This was missing, although nobody seems to have notied yet. - "Introduce a store type enum for the Maple tree" from Sidhartha Kumar. Cleanups and modest performance improvements for the maple tree library code. - "memcg: further decouple v1 code from v2" from Shakeel Butt. Move more cgroup v1 remnants away from the v2 memcg code. - "memcg: initiate deprecation of v1 features" from Shakeel Butt. Adds various warnings telling users that memcg v1 features are deprecated. - "mm: swap: mTHP swap allocator base on swap cluster order" from Chris Li. Greatly improves the success rate of the mTHP swap allocation. - "mm: introduce numa_memblks" from Mike Rapoport. Moves various disparate per-arch implementations of numa_memblk code into generic code. - "mm: batch free swaps for zap_pte_range()" from Barry Song. Greatly improves the performance of munmap() of swap-filled ptes. - "support large folio swap-out and swap-in for shmem" from Baolin Wang. With this series we no longer split shmem large folios into simgle-page folios when swapping out shmem. - "mm/hugetlb: alloc/free gigantic folios" from Yu Zhao. Nice performance improvements and code reductions for gigantic folios. - "support shmem mTHP collapse" from Baolin Wang. Adds support for khugepaged's collapsing of shmem mTHP folios. - "mm: Optimize mseal checks" from Pedro Falcato. Fixes an mprotect() performance regression due to the addition of mseal(). - "Increase the number of bits available in page_type" from Matthew Wilcox. Increases the number of bits available in page_type! - "Simplify the page flags a little" from Matthew Wilcox. Many legacy page flags are now folio flags, so the page-based flags and their accessors/mutators can be removed. - "mm: store zero pages to be swapped out in a bitmap" from Usama Arif. An optimization which permits us to avoid writing/reading zero-filled zswap pages to backing store. - "Avoid MAP_FIXED gap exposure" from Liam Howlett. Fixes a race window which occurs when a MAP_FIXED operqtion is occurring during an unrelated vma tree walk. - "mm: remove vma_merge()" from Lorenzo Stoakes. Major rotorooting of the vma_merge() functionality, making ot cleaner, more testable and better tested. - "misc fixups for DAMON {self,kunit} tests" from SeongJae Park. Minor fixups of DAMON selftests and kunit tests. - "mm: memory_hotplug: improve do_migrate_range()" from Kefeng Wang. Code cleanups and folio conversions. - "Shmem mTHP controls and stats improvements" from Ryan Roberts. Cleanups for shmem controls and stats. - "mm: count the number of anonymous THPs per size" from Barry Song. Expose additional anon THP stats to userspace for improved tuning. - "mm: finish isolate/putback_lru_page()" from Kefeng Wang: more folio conversions and removal of now-unused page-based APIs. - "replace per-quota region priorities histogram buffer with per-context one" from SeongJae Park. DAMON histogram rationalization. - "Docs/damon: update GitHub repo URLs and maintainer-profile" from SeongJae Park. DAMON documentation updates. - "mm/vdpa: correct misuse of non-direct-reclaim __GFP_NOFAIL and improve related doc and warn" from Jason Wang: fixes usage of page allocator __GFP_NOFAIL and GFP_ATOMIC flags. - "mm: split underused THPs" from Yu Zhao. Improve THP=always policy. This was overprovisioning THPs in sparsely accessed memory areas. - "zram: introduce custom comp backends API" frm Sergey Senozhatsky. Add support for zram run-time compression algorithm tuning. - "mm: Care about shadow stack guard gap when getting an unmapped area" from Mark Brown. Fix up the various arch_get_unmapped_area() implementations to better respect guard areas. - "Improve mem_cgroup_iter()" from Kinsey Ho. Improve the reliability of mem_cgroup_iter() and various code cleanups. - "mm: Support huge pfnmaps" from Peter Xu. Extends the usage of huge pfnmap support. - "resource: Fix region_intersects() vs add_memory_driver_managed()" from Huang Ying. Fix a bug in region_intersects() for systems with CXL memory. - "mm: hwpoison: two more poison recovery" from Kefeng Wang. Teaches a couple more code paths to correctly recover from the encountering of poisoned memry. - "mm: enable large folios swap-in support" from Barry Song. Support the swapin of mTHP memory into appropriately-sized folios, rather than into single-page folios" * tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (416 commits) zram: free secondary algorithms names uprobes: turn xol_area->pages[2] into xol_area->page uprobes: introduce the global struct vm_special_mapping xol_mapping Revert "uprobes: use vm_special_mapping close() functionality" mm: support large folios swap-in for sync io devices mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios mm: fix swap_read_folio_zeromap() for large folios with partial zeromap mm/debug_vm_pgtable: Use pxdp_get() for accessing page table entries set_memory: add __must_check to generic stubs mm/vma: return the exact errno in vms_gather_munmap_vmas() memcg: cleanup with !CONFIG_MEMCG_V1 mm/show_mem.c: report alloc tags in human readable units mm: support poison recovery from copy_present_page() mm: support poison recovery from do_cow_fault() resource, kunit: add test case for region_intersects() resource: make alloc_free_mem_region() works for iomem_resource mm: z3fold: deprecate CONFIG_Z3FOLD vfio/pci: implement huge_fault support mm/arm64: support large pfn mappings mm/x86: support large pfn mappings ...

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: clean up mem_cgroup_iter()

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

A clean up to make variable names more clear and to improve code readability. No functional change. Link: https://lkml.kernel.org/r/20240905003058.1859929-6-kinseyho@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: 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