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Date: Mon, 20 Oct 2014 11:18:38 -0400
From: Rik van Riel <riel@redhat.com>
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To: Vlastimil Babka <vbabka@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>
CC: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Minchan Kim <minchan@kernel.org>, Mel Gorman <mgorman@suse.de>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Michal Nazarewicz <mina86@mina86.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Christoph Lameter <cl@linux.com>, David Rientjes <rientjes@google.com>
Subject: Re: [PATCH 3/5] mm, compaction: defer only on COMPACT_COMPLETE
References: <1412696019-21761-1-git-send-email-vbabka@suse.cz> <1412696019-21761-4-git-send-email-vbabka@suse.cz>
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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@suse.cz>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: David Rientjes <rientjes@google.com>

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