linux-kernel - Re: [PATCH V4 09/15] mm, compaction: skip rechecks when lock was already held

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Date:	Fri, 25 Jul 2014 13:34:13 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org,
	Michal Nazarewicz <mina86@...a86.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Minchan Kim <minchan@...nel.org>,
	Zhang Yanfei <zhangyanfei@...fujitsu.com>
Subject: Re: [PATCH V4 09/15] mm, compaction: skip rechecks when lock was
 already held

On Wed, Jul 16, 2014 at 03:48:17PM +0200, Vlastimil Babka wrote:
> Compaction scanners try to lock zone locks as late as possible by checking
> many page or pageblock properties opportunistically without lock and skipping
> them if not unsuitable. For pages that pass the initial checks, some properties
> have to be checked again safely under lock. However, if the lock was already
> held from a previous iteration in the initial checks, the rechecks are
> unnecessary.
> 
> This patch therefore skips the rechecks when the lock was already held. This is
> now possible to do, since we don't (potentially) drop and reacquire the lock
> between the initial checks and the safe rechecks anymore.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Reviewed-by: Zhang Yanfei <zhangyanfei@...fujitsu.com>
> Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Acked-by: Minchan Kim <minchan@...nel.org>
> Cc: Mel Gorman <mgorman@...e.de>
> 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>
> Acked-by: David Rientjes <rientjes@...gle.com>

Acked-by: Mel Gorman <mgorman@...e.de>

-- 
Mel Gorman
SUSE Labs
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