linux-kernel - Re: [PATCH 3/5] mm, compaction: defer only on COMPACT

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Message-ID: <544527CE.8090607@redhat.com>
Date:	Mon, 20 Oct 2014 11:18:38 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Minchan Kim <minchan@...nel.org>, Mel Gorman <mgorman@...e.de>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH 3/5] mm, compaction: defer only on COMPACT_COMPLETE

On 10/07/2014 11:33 AM, Vlastimil Babka wrote:
> Deferred compaction is employed to avoid compacting zone where sync direct
> compaction has recently failed. As such, it makes sense to only defer when
> a full zone was scanned, which is when compact_zone returns with
> COMPACT_COMPLETE. It's less useful to defer when compact_zone returns with
> apparent success (COMPACT_PARTIAL), followed by a watermark check failure,
> which can happen due to parallel allocation activity. It also does not make
> much sense to defer compaction which was completely skipped (COMPACT_SKIP) for
> being unsuitable in the first place.
>
> This patch therefore makes deferred compaction trigger only when
> COMPACT_COMPLETE is returned from compact_zone(). Results of stress-highalloc
> becnmark show the difference is within measurement error, so the issue is
> rather cosmetic.
>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: Michal Nazarewicz <mina86@...a86.com>
> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: David Rientjes <rientjes@...gle.com>

Acked-by: Rik van Riel <riel@...hat.com>

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