linux-kernel - Re: OOM detection regressions since 4.7

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Date:   Tue, 23 Aug 2016 09:48:53 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Markus Trippelsdorf <markus@...ppelsdorf.de>
Cc:     Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, greg@...e.cz,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Arkadiusz Miskiewicz <a.miskiewicz@...il.com>,
        Ralf-Peter Rohbeck <Ralf-Peter.Rohbeck@...ntum.com>,
        Jiri Slaby <jslaby@...e.com>, Olaf Hering <olaf@...fle.de>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: OOM detection regressions since 4.7

On Tue 23-08-16 09:40:14, Markus Trippelsdorf wrote:
> On 2016.08.23 at 09:33 +0200, Michal Hocko wrote:
> > On Tue 23-08-16 13:52:45, Joonsoo Kim wrote:
> > [...]
> > > Hello, Michal.
> > > 
> > > I agree with partial revert but revert should be a different form.
> > > Below change try to reuse should_compact_retry() version for
> > > !CONFIG_COMPACTION but it turned out that it also causes regression in
> > > Markus report [1].
> > 
> > I would argue that CONFIG_COMPACTION=n behaves so arbitrary for high
> > order workloads that calling any change in that behavior a regression
> > is little bit exaggerated. Disabling compaction should have a very
> > strong reason. I haven't heard any so far. I am even wondering whether
> > there is a legitimate reason for that these days.
> 
> BTW, the current config description:
> 
>   CONFIG_COMPACTION:
>   Allows the compaction of memory for the allocation of huge pages. 
> 
> doesn't make it clear to the user that this is an essential feature.

Yes I plan to send a clarification patch.
-- 
Michal Hocko
SUSE Labs