linux-kernel - Re: [PATCH 12/14] mm, oom: protect !costly allocations some more

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Message-ID: <20160504085307.GD29978@dhcp22.suse.cz>
Date:	Wed, 4 May 2016 10:53:07 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Hillf Danton <hillf.zj@...baba-inc.com>,
	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 12/14] mm, oom: protect !costly allocations some more

On Wed 04-05-16 15:01:24, Joonsoo Kim wrote:
> On Wed, Apr 20, 2016 at 03:47:25PM -0400, Michal Hocko wrote:
[...]

Please try to trim your responses it makes it much easier to follow the
discussion

> > +static inline bool
> > +should_compact_retry(unsigned int order, enum compact_result compact_result,
> > +		     enum migrate_mode *migrate_mode,
> > +		     int compaction_retries)
> > +{
> > +	if (!order)
> > +		return false;
> > +
> > +	/*
> > +	 * compaction considers all the zone as desperately out of memory
> > +	 * so it doesn't really make much sense to retry except when the
> > +	 * failure could be caused by weak migration mode.
> > +	 */
> > +	if (compaction_failed(compact_result)) {
> 
> IIUC, this compaction_failed() means that at least one zone is
> compacted and failed. This is not same with your assumption in the
> comment. If compaction is done and failed on ZONE_DMA, it would be
> premature decision.

Not really, because if other zones are making some progress then their
result will override COMPACT_COMPLETE

[...]
-- 
Michal Hocko
SUSE Labs