linux-kernel - RE: [PATCH] mm: fix page_mkclean

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Message-ID: <Pine.LNX.4.64.0612280909070.4473@woody.osdl.org>
Date:	Thu, 28 Dec 2006 09:10:42 -0800 (PST)
From:	Linus Torvalds <torvalds@...l.org>
To:	"Chen, Kenneth W" <kenneth.w.chen@...el.com>
cc:	David Miller <davem@...emloft.net>, ranma@...edrich.de,
	gordonfarquharson@...il.com, tbm@...ius.com,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, andrei.popa@...eo.ro,
	Andrew Morton <akpm@...l.org>, hugh@...itas.com,
	nickpiggin@...oo.com.au, arjan@...radead.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] mm: fix page_mkclean_one



On Wed, 27 Dec 2006, Chen, Kenneth W wrote:
> > 
> > Running the test code, git bisect points its finger at this commit. Reverting
> > this commit on top of 2.6.20-rc2 doesn't trigger the bug from the test code.
> > 
> >     [PATCH] mm: balance dirty pages
> > 
> >     Now that we can detect writers of shared mappings, throttle them.  Avoids OOM
> >     by surprise.
> 
> Oh, never mind :-(  I just didn't create enough write out pressure when
> test this. I just saw bug got triggered on a kernel I previously thought
> was OK.

Btw, this is an important point - people have long felt that the new page 
balancing in 2.6.19 was to blame, but you've just confirmed the long-held 
suspicion (at least by me) that it's not actually a new bug at all, it's 
just that the dirty page balancing causes writeback to happen _earlier_, 
and thus is better able to _show_ a bug that we've likely had for a long 
long time.

			Linus
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