linux-kernel - Re: [PATCH 0/3] OOM detection rework v4

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Message-ID: <20160302022846.GB22355@js1304-P5Q-DELUXE>
Date:	Wed, 2 Mar 2016 11:28:46 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Hugh Dickins <hughd@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
	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>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] OOM detection rework v4

On Tue, Mar 01, 2016 at 02:38:46PM +0100, Michal Hocko wrote:
> > I'd expect a build in 224M
> > RAM plus 2G of swap to take so long, that I'd be very grateful to be
> > OOM killed, even if there is technically enough space.  Unless
> > perhaps it's some superfast swap that you have?
> 
> the swap partition is a standard qcow image stored on my SSD disk. So
> I guess the IO should be quite fast. This smells like a potential
> contributor because my reclaim seems to be much faster and that should
> lead to a more efficient reclaim (in the scanned/reclaimed sense).

Hmm... This looks like one of potential culprit. If page is in
writeback, it can't be migrated by compaction with MIGRATE_SYNC_LIGHT.
In this case, this page works as pinned page and prevent compaction.
It'd be better to check that changing 'migration_mode = MIGRATE_SYNC' at
'no_progress_loops > XXX' will help in this situation.

Thanks.