linux-kernel - Re: [PATCH 1/3] Reintroduce zone_reclaim_interval for when zone_reclaim() scans and fails to avoid CPU spinning at 100% on NUMA

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Date:	Mon, 08 Jun 2009 10:48:16 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mel@....ul.ie>
CC:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	yanmin.zhang@...el.com, Wu Fengguang <fengguang.wu@...el.com>,
	linuxram@...ibm.com, linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] Reintroduce zone_reclaim_interval for when	zone_reclaim()
 scans and fails to avoid CPU spinning at 100% on NUMA

Mel Gorman wrote:
> On Mon, Jun 08, 2009 at 09:31:09AM -0400, Rik van Riel wrote:
>> Mel Gorman wrote:
>>
>>> The scanning occurs because zone_reclaim() cannot tell
>>> in advance the scan is pointless because the counters do not distinguish
>>> between pagecache pages backed by disk and by RAM. 
>> Yes it can.  Since 2.6.27, filesystem backed and swap/ram backed
>> pages have been living on separate LRU lists. 
> 
> Yes, they're on separate LRU lists but they are not the only pages on those
> lists. The tmpfs pages are mixed in together with anonymous pages so we
> cannot use NR_*_ANON.
> 
> Look at patch 2 and where I introduced;

I have to admit I did not read patches 2 and 3 before
replying to the (strange looking, at the time) text
above patch 1.

With that logic from patch 2 in place, patch 1 makes
perfect sense.

Acked-by: Rik van Riel <riel@...hat.com>

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