linux-kernel - Re: [PATCH 4/4] capture pages freed during direct reclaim for allocation by the reclaimer

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Date:	Thu, 02 Oct 2008 11:29:32 -0500
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Andy Whitcroft <apw@...dowen.org>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/4] capture pages freed during direct reclaim for	allocation
 by the reclaimer

Andy Whitcroft wrote:

>> At the beginning of reclaim just flush all pcp pages and then do not allow pcp
>> refills again until reclaim is finished?
> 
> Not entirely, some pages could get trapped there for sure.  But it is
> parallel allocations we are trying to guard against.  Plus we already flush
> the pcp during reclaim for higher orders.

So we just would need to forbid refilling the pcp.

Parallel allocations are less a problem if the freed order 0 pages get merged
immediately into the order 1 freelist. Of course that will only work 50% of
the time but it will have a similar effect to this patch.

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