linux-kernel - Re: [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low

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Message-ID: <20101129095618.GB13268@csn.ul.ie>
Date:	Mon, 29 Nov 2010 09:56:19 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Kyle McMartin <kyle@...artin.ca>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Shaohua Li <shaohua.li@...el.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter
	threshold when memory is low

On Fri, Nov 26, 2010 at 11:06:19AM -0500, Kyle McMartin wrote:
> On Wed, Oct 27, 2010 at 09:47:35AM +0100, Mel Gorman wrote:
> ><snip>
> > To ensure that kswapd wakes up, a safe version of zone_watermark_ok()
> > is introduced that takes a more accurate reading of NR_FREE_PAGES when
> > called from wakeup_kswapd, when deciding whether it is really safe to go
> > back to sleep in sleeping_prematurely() and when deciding if a zone is
> > really balanced or not in balance_pgdat(). We are still using an expensive
> > function but limiting how often it is called.
> ><snip>
> > Reported-by: Shaohua Li <shaohua.li@...el.com>
> > Signed-off-by: Mel Gorman <mel@....ul.ie>
> 
> Hi Mel,
> 
> I notice these aren't flagged for stable, should they be? (They fairly
> trivially apply and compile on 2.6.36 barring the trace_ points which
> changed.)

They were not flagged for stable because they were performance rather than
function bugs that affected a limited number of machines. Should that decision
be revisited?

> I've got a few bug reports against .36/.37 where kswapd has
> been sleeping for 60s+.
> 

I do not believe these patches would affect kswapd sleeping for 60s.

> I built them some kernels with these patches, but haven't heard back yet
> as to whether it fixes things for them.
> 
> Thanks for any insight,

Can you point me at a relevant bugzilla entry or forward me the bug report
and I'll take a look?

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