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Commit f56ce412 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds
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mm: memcontrol: fix occasional OOMs due to proportional memory.low reclaim

We've noticed occasional OOM killing when memory.low settings are in
effect for cgroups.  This is unexpected and undesirable as memory.low is
supposed to express non-OOMing memory priorities between cgroups.

The reason for this is proportional memory.low reclaim.  When cgroups
are below their memory.low threshold, reclaim passes them over in the
first round, and then retries if it couldn't find pages anywhere else.
But when cgroups are slightly above their memory.low setting, page scan
force is scaled down and diminished in proportion to the overage, to the
point where it can cause reclaim to fail as well - only in that case we
currently don't retry, and instead trigger OOM.

To fix this, hook proportional reclaim into the same retry logic we have
in place for when cgroups are skipped entirely.  This way if reclaim
fails and some cgroups were scanned with diminished pressure, we'll try
another full-force cycle before giving up and OOMing.

[akpm@linux-foundation.org: coding-style fixes]

Link: https://lkml.kernel.org/r/20210817180506.220056-1-hannes@cmpxchg.org


Fixes: 9783aa99 ("mm, memcg: proportional memory.{low,min} reclaim")
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reported-by: default avatarLeon Yang <lnyng@fb.com>
Reviewed-by: default avatarRik van Riel <riel@surriel.com>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Acked-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarChris Down <chris@chrisdown.name>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>		[5.4+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 91ed3ed0
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