From: Con Kolivas <kernel@kolivas.org>
To: Valdis.Kletnieks@vt.edu
Subject: Re: 2.6.14-rc2-mm1 - ext3 wedging up
Date: Fri, 23 Sep 2005 19:45:36 +1000
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Cc: Andrea Arcangeli <andrea@suse.de>, linux-kernel@vger.kernel.org
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On Fri, 23 Sep 2005 17:20, Valdis.Kletnieks@vt.edu wrote:
> On Fri, 23 Sep 2005 10:36:16 +1000, Con Kolivas said:
>
> (Adding Andrea to the To: list...)
>
> > On Fri, 23 Sep 2005 05:59, Valdis.Kletnieks@vt.edu wrote:
> > > Am seeing reproducible wedging up when writing large (20M+) files to an
> > > ext3 file system.  Oddly enough, if something *else* writes files to
> > > the file system as well, it will unwedge for a while and make progress.
> > >  Also, a 'sync' command will relieve things temporarily - but after a
> > > few megabytes it comes to a halt again.  Looks like a borkage someplace
> > > not causing it to actually finish pushing dirty file pages out -
> > > gkrellm reports little/no disk activity in progress. File activity on
> > > *other* filesystems continues unimpeded.
> >
> > Could be the write throttling patches.
> >
> > Try backing these out (in this order I think):
> >
> > http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.14-rc2
> >/2.6
>
> .14-rc2-mm1/broken-out/per-task-predictive-write-throttling-1-tweaks.patch
>
> > http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.14-rc2
> >/2.6
>
> .14-rc2-mm1/broken-out/per-task-predictive-write-throttling-1.patch
>
> Bingo.  I haven't built a kernel with these excluded, but writing 0 to
> /proc/sys/vm/dirty_ratio_centisecs fixes the problem, so I'm pretty sure
> this is it.
>
> (For the record, I've noticed the starvation issue that Andrea is trying to
> address, where one process can lock out others, so I *do* think work is
> needed here...)

I don't disagree, which is why I was excited by this work as well. Like all 
things in the kernel it always ends up being more complicated than the 
original plan, requiring reworking. So I do not remotely see this as a 
problem at this early stage.

Cheers,
Con
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