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Date: Wed, 4 May 2016 10:53:07 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>, Mel Gorman <mgorman@suse.de>,
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        Hillf Danton <hillf.zj@alibaba-inc.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 12/14] mm, oom: protect !costly allocations some more
Message-ID: <20160504085307.GD29978@dhcp22.suse.cz>
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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