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Subject: Re: 2.4.21-pre2 stalls out when running unixbench
From: "Stephen C. Tweedie" <sct@redhat.com>
To: Andrew Morton <akpm@digeo.com>
Cc: Joe Korty <joe.korty@ccur.com>, Andreas Dilger <adilger@clusterfs.com>,
       rusty@rustcorp.com.au, riel@conectiva.com.br,
       linux-kernel@vger.kernel.org, hch@sgi.com
In-Reply-To: <3E16C171.BFEA45AE@digeo.com>
References: <3E15F2F5.356A933D@digeo.com> from "Andrew Morton" at Jan 03,
	2003 12:30:45 PM <200301040111.BAA00401@rudolph.ccur.com> 
	<3E16C171.BFEA45AE@digeo.com>
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Hi,

On Sat, 2003-01-04 at 11:11, Andrew Morton wrote:

> This is because of differences in how sync() is handled between 2.4.20's
> ext3 and 2.4.21-pre2's.
> 
> 2.4.21-pre2:
> 
>   sync() will start the commit, and will wait on it.  So you know that
>   when it returns, everything which was dirty is now tight on disk.
> 
> So yes, running a looping sync while someone else is writing stuff
> will take much longer in 2.4.21-pre2, because that kernel actually
> waits on the writeout.

Actually, I'm wondering if we should back that particular bit out.  For
a user with a hundred mounted filesystems, syncing each one in order,
sequentially, is going to suck (and we don't currently have a simple way
in 2.4 to detect which syncs are on separate spindles and so can be
parallelised.)

--Stephen

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