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Date: Mon, 08 May 2006 18:18:18 -0700
From: Maxim Sobolev <sobomax@FreeBSD.org>
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To: Kris Kennaway <kris@obsecurity.org>
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Cc: Robert Watson <rwatson@FreeBSD.org>, performance@FreeBSD.org,
	current@FreeBSD.org
Subject: Re: Fine-grained locking for POSIX local sockets (UNIX
	domain	sockets)
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Kris Kennaway wrote:
> On Mon, May 08, 2006 at 02:52:07AM -0400, Kris Kennaway wrote:
>> OK, David's patch fixes the umtx thundering herd (and seems to give a
>> 4-6% boost).  I also fixed a thundering herd in FILEDESC_UNLOCK (which
>> was also waking up 2-7 CPUs at once about 30% of the time) by doing
>> s/wakeup/wakeup_one/.  This did not seem to give a performance impact
>> on this test though.
> 
> Turning down kern.hz from 1000 to 100 also made a big difference on 12
> CPUs (+6.1%).
> 
> Note also that the system is no less than 40% idle during the runs (at
> any load), so the bottlenecks are serious.

Maybe HDD just can't keep up with the pace?

-Maxim