linux-kernel - Re: [Bug 9182] Critical memory leak (dirty pages)

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Date:	Sun, 16 Dec 2007 13:51:12 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Krzysztof Oledzki <olel@....pl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Osterried <osterried@...se.de>, protasnb@...il.com,
	bugme-daemon@...zilla.kernel.org
Subject: Re: [Bug 9182] Critical memory leak (dirty pages)

On Sun, 16 Dec 2007 14:46:36 +0100 (CET) Krzysztof Oledzki <olel@....pl> wrote:

> >>> Which filesystem, which mount options
> >>
> >>   - ext3 on RAID1 (MD): / - rootflags=data=journal
> >
> > It wouldn't surprise me if this is specific to data=journal: that
> > journalling mode is pretty complex wrt dairty-data handling and isn't well
> > tested.
> >
> > Does switching that to data=writeback change things?
> 
> I'll confirm this tomorrow but it seems that even switching to 
> data=ordered (AFAIK default o ext3) is indeed enough to cure this problem.

yes, sorry, I meant ordered.

> Two questions remain then: why system dies when dirty reaches ~200MB 

I think you have ~2G of RAM and you're running with 
/proc/sys/vm/dirty_ratio=10, yes?

If so, when that machine hits 10% * 2G of dirty memory then everyone who
wants to dirty pages gets blocked.

> and what is wrong with ext3+data=journal with >=2.6.20-rc2?

Ah.  It has a bug in it ;)

As I said, data=journal has exceptional handling of pagecache data and is
not well tested.  Someone (and I'm not sure who) will need to get in there
and fix it.
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