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Date: Wed, 18 Jan 2017 10:08:53 +0000 From: Mel Gorman <mgorman@...hsingularity.net> To: Vlastimil Babka <vbabka@...e.cz> Cc: Ganapatrao Kulkarni <gpkulkarni@...il.com>, Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [RFC 4/4] mm, page_alloc: fix premature OOM when racing with cpuset mems update On Tue, Jan 17, 2017 at 11:16:10PM +0100, Vlastimil Babka wrote: > Ganapatrao Kulkarni reported that the LTP test cpuset01 in stress mode triggers > OOM killer in few seconds, despite lots of free memory. The test attemps to > repeatedly fault in memory in one process in a cpuset, while changing allowed > nodes of the cpuset between 0 and 1 in another process. > > The problem comes from insufficient protection against cpuset changes, which > can cause get_page_from_freelist() to consider all zones as non-eligible due to > nodemask and/or current->mems_allowed. This was masked in the past by > sufficient retries, but since commit 682a3385e773 ("mm, page_alloc: inline the > fast path of the zonelist iterator") we fix the preferred_zoneref once, and > don't iterate the whole zonelist in further attempts. > > A previous patch fixed this problem for current->mems_allowed. However, cpuset > changes also update the policy nodemasks. The fix has two parts. We have to > repeat the preferred_zoneref search when we detect cpuset update by way of > seqcount, and we have to check the seqcount before considering OOM. > > Reported-by: Ganapatrao Kulkarni <gpkulkarni@...il.com> > Fixes: 682a3385e773 ("mm, page_alloc: inline the fast path of the zonelist iterator") > Signed-off-by: Vlastimil Babka <vbabka@...e.cz> Acked-by: Mel Gorman <mgorman@...hsingularity.net> -- Mel Gorman SUSE Labs
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