linux-kernel - Re: [PATCH 08/12] Direct compact when a high-order allocation fails

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Message-ID: <4B7CBAB4.2010003@redhat.com>
Date:	Wed, 17 Feb 2010 22:57:40 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mel@....ul.ie>
CC:	Andrea Arcangeli <aarcange@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 08/12] Direct compact when a high-order allocation fails

On 02/12/2010 07:00 AM, Mel Gorman wrote:
> Ordinarily when a high-order allocation fails, direct reclaim is entered to
> free pages to satisfy the allocation.  With this patch, it is determined if
> an allocation failed due to external fragmentation instead of low memory
> and if so, the calling process will compact until a suitable page is
> freed. Compaction by moving pages in memory is considerably cheaper than
> paging out to disk and works where there are locked pages or no swap. If
> compaction fails to free a page of a suitable size, then reclaim will
> still occur.
>
> Direct compaction returns as soon as possible. As each block is compacted,
> it is checked if a suitable page has been freed and if so, it returns.
>
> Signed-off-by: Mel Gorman<mel@....ul.ie>

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

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