linux-kernel - Re: [PATCH 6/9] mm: compaction: Acquire the zone->lock as late as possible

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Message-ID: <20120925073557.GM13234@bbox>
Date:	Tue, 25 Sep 2012 16:35:57 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Richard Davies <richard@...chsys.com>,
	Shaohua Li <shli@...nel.org>, Rik van Riel <riel@...hat.com>,
	Avi Kivity <avi@...hat.com>,
	QEMU-devel <qemu-devel@...gnu.org>, KVM <kvm@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/9] mm: compaction: Acquire the zone->lock as late as
 possible

On Fri, Sep 21, 2012 at 11:46:20AM +0100, Mel Gorman wrote:
> Compactions free scanner acquires the zone->lock when checking for PageBuddy
> pages and isolating them. It does this even if there are no PageBuddy pages
> in the range.
> 
> This patch defers acquiring the zone lock for as long as possible. In the
> event there are no free pages in the pageblock then the lock will not be
> acquired at all which reduces contention on zone->lock.
> 
> Signed-off-by: Mel Gorman <mgorman@...e.de>
> Acked-by: Rik van Riel <riel@...hat.com>
Acked-by: Minchan Kim <minchan@...nel.org>

-- 
Kind regards,
Minchan Kim
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