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Roman Gushchin 172b06c32b mm: slowly shrink slabs with a relatively small number of objects 
9092c71bb7 ("mm: use sc->priority for slab shrink targets") changed the
way that the target slab pressure is calculated and made it
priority-based:

    delta = freeable >> priority;
    delta *= 4;
    do_div(delta, shrinker->seeks);

The problem is that on a default priority (which is 12) no pressure is
applied at all, if the number of potentially reclaimable objects is less
than 4096 (1<<12).

This causes the last objects on slab caches of no longer used cgroups to
(almost) never get reclaimed.  It's obviously a waste of memory.

It can be especially painful, if these stale objects are holding a
reference to a dying cgroup.  Slab LRU lists are reparented on memcg
offlining, but corresponding objects are still holding a reference to the
dying cgroup.  If we don't scan these objects, the dying cgroup can't go
away.  Most likely, the parent cgroup hasn't any directly charged objects,
only remaining objects from dying children cgroups.  So it can easily hold
a reference to hundreds of dying cgroups.

If there are no big spikes in memory pressure, and new memory cgroups are
created and destroyed periodically, this causes the number of dying
cgroups grow steadily, causing a slow-ish and hard-to-detect memory
"leak".  It's not a real leak, as the memory can be eventually reclaimed,
but it could not happen in a real life at all.  I've seen hosts with a
steadily climbing number of dying cgroups, which doesn't show any signs of
a decline in months, despite the host is loaded with a production
workload.

It is an obvious waste of memory, and to prevent it, let's apply a minimal
pressure even on small shrinker lists.  E.g.  if there are freeable
objects, let's scan at least min(freeable, scan_batch) objects.

This fix significantly improves a chance of a dying cgroup to be
reclaimed, and together with some previous patches stops the steady growth
of the dying cgroups number on some of our hosts.

Link: http://lkml.kernel.org/r/20180905230759.12236-1-guro@fb.com
Fixes: 9092c71bb7 ("mm: use sc->priority for slab shrink targets")
Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Rik van Riel <riel@surriel.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2018-09-20 22:01:11 +02:00
..
kasan kernel/memremap, kasan: make ZONE_DEVICE with work with KASAN 2018-08-17 16:20:30 -07:00
Kconfig mm: disable deferred struct page for 32-bit arches 2018-09-20 22:01:11 +02:00
Kconfig.debug mm: clarify CONFIG_PAGE_POISONING and usage 2018-08-22 10:52:44 -07:00
Makefile vfs: implement readahead(2) using POSIX_FADV_WILLNEED 2018-08-30 20:01:32 +02:00
backing-dev.c blkcg: delay blkg destruction until after writeback has finished 2018-08-31 14:48:56 -06:00
balloon_compaction.c virtio_balloon: fix deadlock on OOM 2017-11-14 23:57:38 +02:00
bootmem.c docs/mm: bootmem: add overview documentation 2018-08-02 12:17:27 -06:00
cleancache.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
cma.c mm/cma: remove unsupported gfp_mask parameter from cma_alloc() 2018-08-17 16:20:32 -07:00
cma.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cma_debug.c mm/cma: remove unsupported gfp_mask parameter from cma_alloc() 2018-08-17 16:20:32 -07:00
compaction.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
debug.c mm: get rid of vmacache_flush_all() entirely 2018-09-13 15:18:04 -10:00
debug_page_ref.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dmapool.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
early_ioremap.c mm/early_ioremap: Fix boot hang with earlyprintk=efi,keep 2017-12-11 14:54:44 +01:00
fadvise.c vfs: implement readahead(2) using POSIX_FADV_WILLNEED 2018-08-30 20:01:32 +02:00
failslab.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
filemap.c mm: use new return type vm_fault_t 2018-06-07 17:34:36 -07:00
frame_vector.c mm/frame_vector.c: release a semaphore in 'get_vaddr_frames()' 2017-12-14 16:00:48 -08:00
frontswap.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
gup.c mm: Change return type int to vm_fault_t for fault handlers 2018-08-23 18:48:44 -07:00
gup_benchmark.c treewide: kvzalloc() -> kvcalloc() 2018-06-12 16:19:22 -07:00
highmem.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
hmm.c libnvdimm-for-4.19_dax-memory-failure 2018-08-25 18:43:59 -07:00
huge_memory.c mm: fix BUG_ON() in vmf_insert_pfn_pud() from VM_MIXEDMAP removal 2018-09-04 16:45:02 -07:00
hugetlb.c mm: Change return type int to vm_fault_t for fault handlers 2018-08-23 18:48:44 -07:00
hugetlb_cgroup.c mm: rename page_counter's count/limit into usage/max 2018-06-07 17:34:35 -07:00
hwpoison-inject.c mm/memory_failure: Remove unused trapno from memory_failure 2018-01-23 12:17:42 -06:00
init-mm.c mm: Allocate the mm_cpumask (mm->cpu_bitmap[]) dynamically based on nr_cpu_ids 2018-07-17 09:35:30 +02:00
internal.h mm: Change return type int to vm_fault_t for fault handlers 2018-08-23 18:48:44 -07:00
interval_tree.c mm/interval_tree.c: use vma_pages() helper 2018-01-31 17:18:37 -08:00
khugepaged.c mm: Change return type int to vm_fault_t for fault handlers 2018-08-23 18:48:44 -07:00
kmemleak-test.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
kmemleak.c kmemleak: always register debugfs file 2018-09-04 16:45:02 -07:00
ksm.c include/linux/compiler*.h: make compiler-*.h mutually exclusive 2018-08-22 17:31:34 -07:00
list_lru.c mm/list_lru: introduce list_lru_shrink_walk_irq() 2018-08-17 16:20:32 -07:00
maccess.c mm: docs: fix parameter names mismatch 2018-02-06 18:32:48 -08:00
madvise.c mm, madvise_inject_error: Let memory_failure() optionally take a page reference 2018-07-23 10:38:05 -07:00
memblock.c mm/memblock.c: replace u64 with phys_addr_t where appropriate 2018-08-17 16:20:30 -07:00
memcontrol.c mm: memcontrol: print proper OOM header when no eligible victim left 2018-09-04 16:45:02 -07:00
memfd.c alloc_file(): switch to passing O_... flags instead of FMODE_... mode 2018-07-12 10:02:57 -04:00
memory-failure.c libnvdimm-for-4.19_dax-memory-failure 2018-08-25 18:43:59 -07:00
memory.c mm/cow: don't bother write protecting already write-protected pages 2018-08-25 13:15:03 -07:00
memory_hotplug.c mm/hugetlb: filter out hugetlb pages if HUGEPAGE migration is not supported. 2018-09-04 16:45:02 -07:00
mempolicy.c mm: access zone->node via zone_to_nid() and zone_set_nid() 2018-08-22 10:52:45 -07:00
mempool.c mm/mempool.c: add missing parameter description 2018-08-22 10:52:44 -07:00
memtest.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
migrate.c mm: soft-offline: close the race against page allocation 2018-08-23 18:48:43 -07:00
mincore.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mlock.c dax: remove VM_MIXEDMAP for fsdax and device dax 2018-08-17 16:20:27 -07:00
mm_init.c mm: access zone->node via zone_to_nid() and zone_set_nid() 2018-08-22 10:52:45 -07:00
mmap.c mm, oom: remove oom_lock from oom_reaper 2018-08-22 10:52:44 -07:00
mmu_context.c sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h> 2017-03-02 08:42:38 +01:00
mmu_notifier.c mm, oom: distinguish blockable mode for mmu notifiers 2018-08-22 10:52:44 -07:00
mmzone.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mprotect.c x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings 2018-06-20 19:10:01 +02:00
mremap.c mremap: remove LATENCY_LIMIT from mremap to reduce the number of TLB shootdowns 2018-06-15 07:55:24 +09:00
msync.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nobootmem.c mm/memblock: add a name for memblock flags enumeration 2018-08-02 12:17:27 -06:00
nommu.c mm: provide a fallback for PAGE_KERNEL_EXEC for architectures 2018-08-17 16:20:29 -07:00
oom_kill.c mm, oom: fix missing tlb_finish_mmu() in __oom_reap_task_mm(). 2018-09-04 16:45:02 -07:00
page-writeback.c notifier: Remove notifier header file wherever not used 2018-08-30 12:56:40 +02:00
page_alloc.c mm/hugetlb: filter out hugetlb pages if HUGEPAGE migration is not supported. 2018-09-04 16:45:02 -07:00
page_counter.c memcg: introduce memory.min 2018-06-07 17:34:36 -07:00
page_ext.c mm/page_ext.c: constify lookup_page_ext() argument 2018-08-17 16:20:28 -07:00
page_idle.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
page_io.c swap,blkcg: issue swap io with the appropriate context 2018-07-09 09:07:54 -06:00
page_isolation.c mm, migrate: remove reason argument from new_page_t 2018-04-11 10:28:32 -07:00
page_owner.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
page_poison.c mm/page_poison.c: make early_page_poison_param() __init 2018-04-05 21:36:26 -07:00
page_vma_mapped.c mm, page_vma_mapped: Introduce pfn_in_hpage() 2018-01-22 12:15:57 -08:00
pagewalk.c mm: kernel-doc: add missing parameter descriptions 2018-04-05 21:36:27 -07:00
percpu-internal.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
percpu-km.c percpu: allow select gfp to be passed to underlying allocators 2018-02-18 05:33:01 -08:00
percpu-stats.c treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
percpu-vm.c percpu: allow select gfp to be passed to underlying allocators 2018-02-18 05:33:01 -08:00
percpu.c /proc/meminfo: add percpu populated pages count 2018-08-22 10:52:45 -07:00
pgtable-generic.c mm: do not lose dirty and accessed bits in pmdp_invalidate() 2018-01-31 17:18:38 -08:00
process_vm_access.c mm: docs: add blank lines to silence sphinx "Unexpected indentation" errors 2018-02-06 18:32:48 -08:00
quicklist.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
readahead.c vfs: implement readahead(2) using POSIX_FADV_WILLNEED 2018-08-30 20:01:32 +02:00
rmap.c mm: do not drop unused pages when userfaultd is running 2018-07-14 11:11:09 -07:00
rodata_test.c mm: fix RODATA_TEST failure "rodata_test: test data was not read only" 2017-10-03 17:54:24 -07:00
shmem.c mm: shmem.c: Correctly annotate new inodes for lockdep 2018-09-20 22:01:11 +02:00
slab.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
slab.h mm: introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB 2018-08-17 16:20:30 -07:00
slab_common.c mm: introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB 2018-08-17 16:20:30 -07:00
slob.c slab: __GFP_ZERO is incompatible with a constructor 2018-06-07 17:34:34 -07:00
slub.c notifier: Remove notifier header file wherever not used 2018-08-30 12:56:40 +02:00
sparse-vmemmap.c mm/sparse: delete old sparse_init and enable new one 2018-08-17 16:20:32 -07:00
sparse.c mm/sparse: delete old sparse_init and enable new one 2018-08-17 16:20:32 -07:00
swap.c mm: introduce MEMORY_DEVICE_FS_DAX and CONFIG_DEV_PAGEMAP_OPS 2018-05-22 06:59:39 -07:00
swap_cgroup.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
swap_slots.c mm, swap, get_swap_pages: use entry_size instead of cluster in parameter 2018-08-22 10:52:44 -07:00
swap_state.c treewide: kvzalloc() -> kvcalloc() 2018-06-12 16:19:22 -07:00
swapfile.c mm/swapfile.c: put_swap_page: share more between huge/normal code path 2018-08-22 10:52:44 -07:00
truncate.c page cache: use xa_lock 2018-04-11 10:28:39 -07:00
usercopy.c usercopy: Allow boot cmdline disabling of hardening 2018-07-04 08:04:52 -07:00
userfaultfd.c userfaultfd: prevent non-cooperative events vs mcopy_atomic races 2018-06-07 17:34:38 -07:00
util.c mm/util.c: improve kvfree() kerneldoc 2018-09-04 16:45:02 -07:00
vmacache.c mm: get rid of vmacache_flush_all() entirely 2018-09-13 15:18:04 -10:00
vmalloc.c mm: provide a fallback for PAGE_KERNEL_EXEC for architectures 2018-08-17 16:20:29 -07:00
vmpressure.c mm/vmpressure.c: convert to use match_string() helper 2018-06-07 17:34:36 -07:00
vmscan.c mm: slowly shrink slabs with a relatively small number of objects 2018-09-20 22:01:11 +02:00
vmstat.c Revert mm/vmstat.c: fix vmstat_update() preemption BUG 2018-06-28 11:16:44 -07:00
workingset.c mm/list_lru: introduce list_lru_shrink_walk_irq() 2018-08-17 16:20:32 -07:00
z3fold.c z3fold: fix reclaim lock-ups 2018-05-11 17:28:45 -07:00
zbud.c mm: docs: fix parameter names mismatch 2018-02-06 18:32:48 -08:00
zpool.c mm/zpool.c: zpool_evictable: fix mismatch in parameter name and kernel-doc 2018-02-21 15:35:43 -08:00
zsmalloc.c mm/zsmalloc.c: make several functions and a struct static 2018-08-17 16:20:30 -07:00
zswap.c zswap: re-check zswap_is_full() after do zswap_shrink() 2018-07-26 19:38:03 -07:00