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From: Robert Watson <rwatson@FreeBSD.org>
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To: Max Laier <max@love2party.net>
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Cc: freebsd-net@freebsd.org, freebsd-current@freebsd.org
Subject: Re: Switch pfil(9) to rmlocks
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On Fri, 23 Nov 2007, Max Laier wrote:

> attached is a diff to switch the pfil(9) subsystem to rmlocks, which are 
> more suited for the task.  I'd like some exposure before doing the switch, 
> but I don't expect any fallout.  This email is going through the patched 
> pfil already - twice.

Max,

Have you done performance measurements that show rmlocks to be a win in this 
scenario?  I did some patchs for UNIX domain sockets to replace the rwlock 
there but it appeared not to have a measurable impact on SQL benchmarks, 
presumbaly because the read/write blend wasn't right and/or that wasnt a 
significant source of overhead in the benchmark.  I'd anticipate a much more 
measurable improvement for pfil, but would be interested in learning how much 
is seen?

Robert N M Watson
Computer Laboratory
University of Cambridge