linux-kernel - Re: [PATCH 3/3] vmscan: Force kswapd to take notice faster when high-order watermarks are being hit

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Message-Id: <200911021832.59035.elendil@planet.nl>
Date:	Mon, 2 Nov 2009 18:32:54 +0100
From:	Frans Pop <elendil@...net.nl>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, stable@...nel.org,
	linux-kernel@...r.kernel.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Sven Geggus <lists@...hsschwanzdomain.de>,
	Karol Lewandowski <karol.k.lewandowski@...il.com>,
	Tobias Oetiker <tobi@...iker.ch>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Stephan von Krawczynski <skraw@...net.com>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: [PATCH 3/3] vmscan: Force kswapd to take notice faster when high-order watermarks are being hit

On Monday 02 November 2009, Mel Gorman wrote:
> vmscan: Help debug kswapd issues by counting number of rewakeups and
> premature sleeps
>
> There is a growing amount of anedotal evidence that high-order atomic
> allocation failures have been increasing since 2.6.31-rc1. The two
> strongest possibilities are a marked increase in the number of
> GFP_ATOMIC allocations and alterations in timing. Debugging printk
> patches have shown for example that kswapd is sleeping for shorter
> intervals and going to sleep when watermarks are still not being met.
>
> This patch adds two kswapd counters to help identify if timing is an
> issue. The first counter kswapd_highorder_rewakeup counts the number of
> times that kswapd stops reclaiming at one order and restarts at a higher
> order. The second counter kswapd_slept_prematurely counts the number of
> times kswapd went to sleep when the high watermark was not met.

What testing would you like done with this patch?
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