On Tue, Aug 17, 2021 at 02:05:06PM -0400, Johannes Weiner wrote:

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 slighly 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 dimished pressure,
we'll try another full-force cycle before giving up and OOMing.

Reported-by: Leon Yang <redacted>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Roman Gushchin <redacted>

I guess it's a stable material, so maybe adding:
Fixes: 9783aa9917f8 ("mm, memcg: proportional memory.{low,min} reclaim")

?


Thanks!