From: Marc Lehmann <schmorp@schmorp.de>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: drastic changes to allocsize semantics in or around 2.6.38?
Date: Fri, 20 May 2011 17:49:20 +0200 [thread overview]
Message-ID: <20110520154920.GD5828@schmorp.de> (raw)
In-Reply-To: <20110520025659.GO32466@dastard>
On Fri, May 20, 2011 at 12:56:59PM +1000, Dave Chinner <david@fromorbit.com> wrote:
[thanks for the thorough explanation]
>
> So the question there: how is your workload accessing the files? Is
> it opening and closing them multiple times in quick succession after
> writing them?
I don't think so, but of course, when compiling a file, it will be linked
afterwards, so I guess it would be accessed at least once.
> I think it is triggering the "NFS server access pattern" logic and so
> keeping speculative preallocation around for longer.
Longer meaning practically infinitely :)
> I'd suggest removing the allocsize mount option - you shouldn't need
> it anymore because the new default behaviour resists fragmentation a
> whole lot better than pre-2.6.38 kernels.
I did remove it already, and will actively try this on our production
server which suffer from severe fragmentation (but xfs_fsr fixes that with
some work (suspending the logfile writing) anyway).
However, I would suggest that whatever heuristic 2.6.38 uses is deeply
broken at the momment, as NFS was not involved here at all (so no need for
it), the usage pattern was a simple compile-then-link-pattern (which is
very common), and there is really no need to cache this preallocation for
files that have been closed 8 hours ago and never touched since then.
--
The choice of a Deliantra, the free code+content MORPG
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----==-- _ generation
---==---(_)__ __ ____ __ Marc Lehmann
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next prev parent reply other threads:[~2011-05-20 15:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-20 0:55 drastic changes to allocsize semantics in or around 2.6.38? Marc Lehmann
2011-05-20 2:56 ` Dave Chinner
2011-05-20 15:49 ` Marc Lehmann [this message]
2011-05-21 0:45 ` Dave Chinner
2011-05-21 1:36 ` Marc Lehmann
2011-05-21 3:15 ` Dave Chinner
2011-05-21 4:16 ` Marc Lehmann
2011-05-22 2:00 ` Dave Chinner
2011-05-22 7:59 ` Matthias Schniedermeyer
2011-05-23 1:20 ` Dave Chinner
2011-05-23 9:01 ` Christoph Hellwig
2011-05-24 0:20 ` Dave Chinner
2011-05-23 13:35 ` Marc Lehmann
2011-05-24 1:30 ` Dave Chinner
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