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From: David Xu <davidxu@freebsd.org>
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Date: Mon, 3 Jul 2006 08:37:04 +0800
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Subject: Re: Updated fine-grain locking patch for UNIX domain sockets
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On Friday 30 June 2006 07:14, Robert Watson wrote:
> Attached, and at the below URL, find an updated copy of the UNIX domain
> socket fine-grained locking patch.  Since the last revision, I've updated
> the patch to close several race conditions historically present in UNIX
> domain sockets (which should be merged regardless of the rest of the
> patch), as well as move to an rwlock for the global lock.
>
>     
> http://www.watson.org/~robert/freebsd/netperf/20060630-uds-fine-grain.diff
>
> This patch increases locking overhead, but decreases contention.  Depending
> on the number of CPUs, it may improve (or not) performance to varying
> degrees; very good reports on sun4v; middling reports on 2-proc, etc. 
> Stability and performance results for UNIX domain socket sensitive
> workloads, such as MySQL, X11, etc, would be appreciated.  Micro-benchmark
> performance should show a small loss, but load under contention and
> scalability are (ideally) improved.
>
> Robert N M Watson
> Computer Laboratory
> University of Cambridge
>

I found 5% performance decrease on dual P4, maybe P4 is quite bad when
doing atomic operation. ;-)
Thanks,

David Xu