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: <20091102173837.GB22046@csn.ul.ie>
Date:	Mon, 2 Nov 2009 17:38:38 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Frans Pop <elendil@...net.nl>
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 Mon, Nov 02, 2009 at 06:32:54PM +0100, Frans Pop wrote:
> 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?
> 

Same reproduction as before except post what the contents of
/proc/vmstat were after the problem was triggered.

Thanks

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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