On Sun, 29 Sept 2024 at 19:26, Jingxiang Zeng <jingxiangzeng.cas@xxxxxxxxx> wrote: > > From: Zeng Jingxiang <linuszeng@xxxxxxxxxxx> There are some formatting issues with the title of this patch, please refer to the latest updated patch: https://lore.kernel.org/all/20240929113050.76079-1-jingxiangzeng.cas@xxxxxxxxx/ > > 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 mem cgroups is about > to OOM due to dirty caches. > > --- > Changes from v3: > - Avoid taking lock and reduce overhead on folio isolation by > checking the right flags and rework wake up condition, fixing the > performance regression reported by Chris Li. > [Chris Li, Kairui Song] > - Move the wake up check to try_to_shrink_lruvec to cover kswapd > case as well, and update comments. [Kairui Song] > - Link to v3: https://lore.kernel.org/all/20240924121358.30685-1-jingxiangzeng.cas@xxxxxxxxx/ > Changes from v2: > - Acquire the lock before calling the folio_check_dirty_writeback > function. [Wei Xu, Jingxiang Zeng] > - Link to v2: https://lore.kernel.org/all/20240913084506.3606292-1-jingxiangzeng.cas@xxxxxxxxx/ > Changes from v1: > - Add code to count the number of unqueued_dirty in the sort_folio > function. [Wei Xu, Jingxiang Zeng] > - Link to v1: https://lore.kernel.org/all/20240829102543.189453-1-jingxiangzeng.cas@xxxxxxxxx/ > --- > > Fixes: 14aa8b2d5c2e ("mm/mglru: don't sync disk for each aging cycle") > 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> > --- > mm/vmscan.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index dc7a285b256b..2a5c2fe81467 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4291,6 +4291,7 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c > 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); > @@ -4336,9 +4337,14 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c > return true; > } > > + dirty = folio_test_dirty(folio); > + writeback = folio_test_writeback(folio); > + if (type == LRU_GEN_FILE && dirty && !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; > @@ -4454,7 +4460,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc, > trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH, > scanned, skipped, isolated, > type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON); > - > + sc->nr.taken += scanned; > /* > * There might not be eligible folios due to reclaim_idx. Check the > * remaining to prevent livelock if it's not making progress. > @@ -4796,6 +4802,13 @@ static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > 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.taken) > + wakeup_flusher_threads(WB_REASON_VMSCAN); > + > /* whether this lruvec should be rotated */ > return nr_to_scan < 0; > } > -- > 2.43.5 >
