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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Message-ID: <4A2D129D.3020309@redhat.com>
Date:	Mon, 08 Jun 2009 09:31:09 -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:

> 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.  This allows you to
fix the underlying problem, instead of having to add a retry
interval.

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