The patch titled
Subject: mm/vmscan: wake up flushers conditionally to avoid cgroup OOM
has been added to the -mm mm-unstable branch. Its filename is
mm-vmscan-wake-up-flushers-conditionally-to-avoid-cgroup-oom.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmscan-wake-up-flushers-conditionally-to-avoid-cgroup-oom.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zeng Jingxiang <linuszeng@xxxxxxxxxxx>
Subject: mm/vmscan: wake up flushers conditionally to avoid cgroup OOM
Date: Sat, 26 Oct 2024 19:57:14 +0800
Commit 14aa8b2d5c2e ("mm/mglru: don't sync disk for each aging cycle")
removed the opportunity to wake up flushers during the MGLRU page
reclamation process can lead to an increased likelihood of triggering OOM
when encountering many dirty pages during reclamation on MGLRU.
This leads to premature OOM if there are too many dirty pages in cgroup:
Killed
dd invoked oom-killer: gfp_mask=0x101cca(GFP_HIGHUSER_MOVABLE|__GFP_WRITE),
order=0, oom_score_adj=0
Call Trace:
<TASK>
dump_stack_lvl+0x5f/0x80
dump_stack+0x14/0x20
dump_header+0x46/0x1b0
oom_kill_process+0x104/0x220
out_of_memory+0x112/0x5a0
mem_cgroup_out_of_memory+0x13b/0x150
try_charge_memcg+0x44f/0x5c0
charge_memcg+0x34/0x50
__mem_cgroup_charge+0x31/0x90
filemap_add_folio+0x4b/0xf0
__filemap_get_folio+0x1a4/0x5b0
? srso_return_thunk+0x5/0x5f
? __block_commit_write+0x82/0xb0
ext4_da_write_begin+0xe5/0x270
generic_perform_write+0x134/0x2b0
ext4_buffered_write_iter+0x57/0xd0
ext4_file_write_iter+0x76/0x7d0
? selinux_file_permission+0x119/0x150
? srso_return_thunk+0x5/0x5f
? srso_return_thunk+0x5/0x5f
vfs_write+0x30c/0x440
ksys_write+0x65/0xe0
__x64_sys_write+0x1e/0x30
x64_sys_call+0x11c2/0x1d50
do_syscall_64+0x47/0x110
entry_SYSCALL_64_after_hwframe+0x76/0x7e
memory: usage 308224kB, limit 308224kB, failcnt 2589
swap: usage 0kB, limit 9007199254740988kB, failcnt 0
...
file_dirty 303247360
file_writeback 0
...
oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=test,
mems_allowed=0,oom_memcg=/test,task_memcg=/test,task=dd,pid=4404,uid=0
Memory cgroup out of memory: Killed process 4404 (dd) total-vm:10512kB,
anon-rss:1152kB, file-rss:1824kB, shmem-rss:0kB, UID:0 pgtables:76kB
oom_score_adj:0
The flusher wake up was removed to decrease SSD wearing, but if we are
seeing all dirty folios at the tail of an LRU, not waking up the flusher
could lead to thrashing easily. So wake it up when a memcg is about to
OOM due to dirty caches.
I did run the build kernel test[1] on V6, with -j16 1G memcg on my local
branch:
Without the patch(10 times):
user 1449.394
system 368.78 372.58 363.03 362.31 360.84 372.70 368.72 364.94 373.51
366.58 (avg 367.399)
real 164.883
With the V6 patch(10 times):
user 1447.525
system 360.87 360.63 372.39 364.09 368.49 365.15 359.93 362.04 359.72
354.60 (avg 362.79)
real 164.514
Test results show that this patch has about 1% performance improvement,
which should be caused by noise.
Link: https://lkml.kernel.org/r/20241026115714.1437435-1-jingxiangzeng.cas@xxxxxxxxx
Link: https://lore.kernel.org/all/CACePvbV4L-gRN9UKKuUnksfVJjOTq_5Sti2-e=pb_w51kucLKQ@xxxxxxxxxxxxxx/ [1]
Fixes: 14aa8b2d5c2e ("mm/mglru: don't sync disk for each aging cycle")
Suggested-by: Wei Xu <weixugc@xxxxxxxxxx>
Signed-off-by: Zeng Jingxiang <linuszeng@xxxxxxxxxxx>
Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
Cc: T.J. Mercier <tjmercier@xxxxxxxxxx>
Cc: Wei Xu <weixugc@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 25 ++++++++++++++++++++++---
1 file changed, 22 insertions(+), 3 deletions(-)
--- a/mm/vmscan.c~mm-vmscan-wake-up-flushers-conditionally-to-avoid-cgroup-oom
+++ a/mm/vmscan.c
@@ -4282,6 +4282,7 @@ static bool sort_folio(struct lruvec *lr
int tier_idx)
{
bool success;
+ bool dirty, writeback;
int gen = folio_lru_gen(folio);
int type = folio_is_file_lru(folio);
int zone = folio_zonenum(folio);
@@ -4327,9 +4328,17 @@ static bool sort_folio(struct lruvec *lr
return true;
}
+ dirty = folio_test_dirty(folio);
+ writeback = folio_test_writeback(folio);
+ if (type == LRU_GEN_FILE && dirty) {
+ sc->nr.file_taken += delta;
+ if (!writeback)
+ sc->nr.unqueued_dirty += delta;
+ }
+
/* waiting for writeback */
- if (folio_test_locked(folio) || folio_test_writeback(folio) ||
- (type == LRU_GEN_FILE && folio_test_dirty(folio))) {
+ if (folio_test_locked(folio) || writeback ||
+ (type == LRU_GEN_FILE && dirty)) {
gen = folio_inc_gen(lruvec, folio, true);
list_move(&folio->lru, &lrugen->folios[gen][type][zone]);
return true;
@@ -4445,7 +4454,8 @@ static int scan_folios(struct lruvec *lr
trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
scanned, skipped, isolated,
type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
-
+ if (type == LRU_GEN_FILE)
+ sc->nr.file_taken += isolated;
/*
* There might not be eligible folios due to reclaim_idx. Check the
* remaining to prevent livelock if it's not making progress.
@@ -4579,6 +4589,7 @@ static int evict_folios(struct lruvec *l
return scanned;
retry:
reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
+ sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
sc->nr_reclaimed += reclaimed;
trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
scanned, reclaimed, &stat, sc->priority,
@@ -4787,6 +4798,13 @@ static bool try_to_shrink_lruvec(struct
cond_resched();
}
+ /*
+ * If too many file cache in the coldest generation can't be evicted
+ * due to being dirty, wake up the flusher.
+ */
+ if (sc->nr.unqueued_dirty && sc->nr.unqueued_dirty == sc->nr.file_taken)
+ wakeup_flusher_threads(WB_REASON_VMSCAN);
+
/* whether this lruvec should be rotated */
return nr_to_scan < 0;
}
@@ -5932,6 +5950,7 @@ static void shrink_node(pg_data_t *pgdat
bool reclaimable = false;
if (lru_gen_enabled() && root_reclaim(sc)) {
+ memset(&sc->nr, 0, sizeof(sc->nr));
lru_gen_shrink_node(pgdat, sc);
return;
}
_
Patches currently in -mm which might be from linuszeng@xxxxxxxxxxx are
mm-memcontrol-add-per-memcg-pgpgin-pswpin-counter.patch
mm-memcontrol-add-per-memcg-pgpgin-pswpin-counter-v2.patch
mm-vmscan-wake-up-flushers-conditionally-to-avoid-cgroup-oom.patch
