Messages in this thread | | | Subject | Re: [PATCH 1/2] vmscan: consider classzone_idx in compaction_ready | From | Vlastimil Babka <> | Date | Mon, 11 Apr 2016 17:24:42 +0200 |
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On 04/11/2016 08:45 AM, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > while playing with the oom detection rework [1] I have noticed > that my heavy order-9 (hugetlb) load close to OOM ended up in an > endless loop where the reclaim hasn't made any progress but > did_some_progress didn't reflect that and compaction_suitable > was backing off because no zone is above low wmark + 1 << order. > > It turned out that this is in fact an old standing bug in compaction_ready > which ignores the requested_highidx and did the watermark check for > 0 classzone_idx. This succeeds for zone DMA most of the time as the zone > is mostly unused because of lowmem protection. This also means that the > OOM killer wouldn't be triggered for higher order requests even when > there is no reclaim progress and we essentially rely on order-0 request > to find this out. This has been broken in one way or another since > fe4b1b244bdb ("mm: vmscan: when reclaiming for compaction, ensure there > are sufficient free pages available") but only since 7335084d446b ("mm: > vmscan: do not OOM if aborting reclaim to start compaction") we are not > invoking the OOM killer based on the wrong calculation. > > Propagate requested_highidx down to compaction_ready and use it for both > the watermak check and compaction_suitable to fix this issue. > > [1] http://lkml.kernel.org/r/1459855533-4600-1-git-send-email-mhocko@kernel.org > Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
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