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Date: Thu, 20 Sep 2012 14:53:59 -0400
From: Rik van Riel <riel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/6] mm: compaction: Abort compaction loop
 if lock is contended or run too long
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To: Mel Gorman <mgorman@suse.de>
Cc: Richard Davies <richard@arachsys.com>, KVM <kvm@vger.kernel.org>, QEMU-devel <qemu-devel@nongnu.org>, LKML <linux-kernel@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>, Avi Kivity <avi@redhat.com>, Shaohua Li <shli@kernel.org>

On 09/20/2012 10:04 AM, Mel Gorman wrote:
> From: Shaohua Li <shli@fusionio.com>
>
> Changelog since V2
> o Fix BUG_ON triggered due to pages left on cc.migratepages
> o Make compact_zone_order() require non-NULL arg `contended'
>
> Changelog since V1
> o only abort the compaction if lock is contended or run too long
> o Rearranged the code by Andrea Arcangeli.
>
> isolate_migratepages_range() might isolate no pages if for example when
> zone->lru_lock is contended and running asynchronous compaction. In this
> case, we should abort compaction, otherwise, compact_zone will run a
> useless loop and make zone->lru_lock is even contended.
>
> [minchan@kernel.org: Putback pages isolated for migration if aborting]
> [akpm@linux-foundation.org: compact_zone_order requires non-NULL arg contended]
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> Signed-off-by: Shaohua Li <shli@fusionio.com>
> Signed-off-by: Mel Gorman <mgorman@suse.de>

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