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From: Gavin Atkinson <gavin@FreeBSD.org>
To: Danny Braniss <danny@cs.huji.ac.il>
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Date: Fri, 26 Sep 2008 13:01:38 +0100
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Cc: freebsd-hackers@FreeBSD.org, freebsd-stable@FreeBSD.org
Subject: Re: bad NFS/UDP performance
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On Fri, 2008-09-26 at 10:04 +0300, Danny Braniss wrote:
> Hi,
> 	There seems to be some serious degradation in performance.
> Under 7.0 I get about 90 MB/s (on write), while, on the same machine
> under 7.1 it drops to 20!
> Any ideas?

The scheduler has been changed to ULE, and NFS has historically been
very sensitive to changes like that.  You could try switching back to
the 4BSD scheduler and seeing if that makes a difference.  If it does,
toggling PREEMPTION would also be interesting to see the results of.

Gavin