linux-kernel - Re: [PATCH 0/4] reintroduce compaction feedback for OOM decisions

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Date:   Wed, 21 Sep 2016 19:18:31 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Arkadiusz Miskiewicz <a.miskiewicz@...il.com>,
        Ralf-Peter Rohbeck <Ralf-Peter.Rohbeck@...ntum.com>,
        Olaf Hering <olaf@...fle.de>, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 0/4] reintroduce compaction feedback for OOM decisions

On Tue 06-09-16 15:52:54, Vlastimil Babka wrote:
> After several people reported OOM's for order-2 allocations in 4.7 due to
> Michal Hocko's OOM rework, he reverted the part that considered compaction
> feedback [1] in the decisions to retry reclaim/compaction. This was to provide
> a fix quickly for 4.8 rc and 4.7 stable series, while mmotm had an almost
> complete solution that instead improved compaction reliability.
> 
> This series completes the mmotm solution and reintroduces the compaction
> feedback into OOM decisions. The first two patches restore the state of mmotm
> before the temporary solution was merged, the last patch should be the missing
> piece for reliability. The third patch restricts the hardened compaction to
> non-costly orders, since costly orders don't result in OOMs in the first place.
> 
> Some preliminary testing suggested that this approach should work, but I would
> like to ask all who experienced the regression to please retest this. You will
> need to apply this series on top of tag mmotm-2016-08-31-16-06 from the mmotm
> git tree [2]. Thanks in advance!

We still do not ignore fragindex in the full priority. This part has
always been quite unclear to me so I cannot really tell whether that
makes any difference or not but just to be on the safe side I would
preffer to have _all_ the shortcuts out of the way in the highest
priority. It is true that this will cause COMPACT_NOT_SUITABLE_ZONE
so keep retrying but still a complication to understand the workflow.

What do you think?
-- 
Michal Hocko
SUSE Labs