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authorJohannes Weiner <hannes@cmpxchg.org>2022-03-22 22:46:30 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-22 23:57:09 +0100
commitd8c47cc7bf602ef73384a00869a70148146c1191 (patch)
tree09f0e453ee6abb35087faee649db6aea406a52b0 /Makefile
parentmemory tiering: skip to scan fast memory (diff)
downloadlinux-d8c47cc7bf602ef73384a00869a70148146c1191.tar.xz
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mm: page_io: fix psi memory pressure error on cold swapins
Once upon a time, all swapins counted toward memory pressure[1]. Then Joonsoo introduced workingset detection for anonymous pages and we gained the ability to distinguish hot from cold swapins[2][3]. But we failed to update swap_readpage() accordingly, and now we account partial memory pressure in the swapin path of cold memory. Not for all situations - which adds more inconsistency: paths using the conventional submit_bio() and lock_page() route will not see much pressure - unless storage itself is heavily congested and the bio submissions stall. ZRAM and ZSWAP do most of the work directly from swap_readpage() and will see all swapins reflected as pressure. IOW, a workload doing cold swapins could see little to no pressure reported with on-disk swap, but potentially high pressure with a zram or zswap backend. That confuses any psi-based health monitoring, load shedding, proactive reclaim, or userspace OOM killing schemes that might be in place for the workload. Restore consistency by making all swapin stall accounting conditional on the page actually being part of the workingset. [1] commit 937790699be9 ("mm/page_io.c: annotate refault stalls from swap_readpage") [2] commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU") [3] commit cad8320b4b39 ("mm/swap: don't SetPageWorkingset unconditionally during swapin") Link: https://lkml.kernel.org/r/20220214214921.419687-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reported-by: CGEL <cgel.zte@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Yu Zhao <yuzhao@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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