linux-kernel - Re: [PATCH 10/11] Direct compact when a high-order allocation fails

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Date:	Thu, 25 Mar 2010 18:50:21 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Minchan Kim <minchan.kim@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 10/11] Direct compact when a high-order allocation fails

On Thu, 25 Mar 2010 09:48:26 +0000
Mel Gorman <mel@....ul.ie> wrote:

> > In that case, compact_finished() can't
> > find there is a free chunk and do more work.  How about using a function like
> > 	 free_pcppages_bulk(zone, pcp->batch, pcp);
> > to bypass pcp list and freeing pages at once ?
> > 
> 
> I think you mean to drain the PCP lists while compaction is happening
> but is it justified? It's potentially a lot of IPI calls just to check
> if compaction can finish a little earlier. If the pages on the PCP lists
> are making that much of a difference to high-order page availability, it
> implies that the zone is pretty full and it's likely that compaction was
> avoided and we direct reclaimed.
> 
Ah, sorry for my short word again. I mean draining "local" pcp list because
a thread which run direct-compaction freed pages. IPI is not necessary and
overkill.

Thanks,
-Kame

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