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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,
       Stephen Tweedie <sct@redhat.com>
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Hi,

On Mon, 2003-01-06 at 12:16, Andrew Morton wrote:

> Well personally I prefer slow-and-safe.  But we could make 2.4
> do what 2.5 is doing - one pass through the superblocks to start
> the syncs and a second pass to wait on them all.

The 2.5 approach has the problem that it can start queuing writeback for
multiple fs'es on the same disk at the same time --- I wouldn't be
surprised if it increases thrashing in that case.  But I guess I'm not
too concerned about sync() performance itself, as long as the in-kernel
background writeback is being done sensibly.

> This is fragile stuff though....

Yep.

--Stephen

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