linux-kernel - Re: [PATCH 7/8] mm: compaction: Use the LRU to get a hint on where compaction should start

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Message-Id: <20101118181048.7bdfbb38.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 18 Nov 2010 18:10:48 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/8] mm: compaction: Use the LRU to get a hint on where
 compaction should start

On Wed, 17 Nov 2010 16:22:48 +0000
Mel Gorman <mel@....ul.ie> wrote:

> The end of the LRU stores the oldest known page. Compaction on the other
> hand always starts scanning from the start of the zone. This patch uses
> the LRU to hint to compaction where it should start scanning from. This
> means that compaction will at least start with some old pages reducing
> the impact on running processes and reducing the amount of scanning. The
> check it makes is racy as the LRU lock is not taken but it should be
> harmless as we are not manipulating the lists without the lock.
> 
> Signed-off-by: Mel Gorman <mel@....ul.ie>

Hmm, does this patch make a noticable difference ?
Isn't it better to start scan from the biggest free chunk in a zone ?

Thanks,
-Kame

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