linux-kernel - Re: [PATCH 04/10] mm, compaction: skip rechecks when lock was already held

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Message-ID: <20140611015020.GE15630@bbox>
Date:	Wed, 11 Jun 2014 10:50:20 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Thelen <gthelen@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Michal Nazarewicz <mina86@...a86.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 04/10] mm, compaction: skip rechecks when lock was
 already held

On Mon, Jun 09, 2014 at 11:26:16AM +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>
Acked-by: Minchan Kim <minchan@...nel.org>

-- 
Kind regards,
Minchan Kim
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