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Date: Thu, 4 Nov 2004 09:05:45 -0500 (EST)
From: Robert Watson <rwatson@freebsd.org>
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To: Poul-Henning Kamp <phk@phk.freebsd.dk>
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cc: arch@freebsd.org
Subject: Re: HEADSUP:  HZ=1000 by default on i386
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On Thu, 4 Nov 2004, Poul-Henning Kamp wrote:

> We increasingly need better granularity in our sleep/wakeup calls and
> things like device polling and trafic shaping needs higher granularity
> in particular. 
> 
> So pending any really good arguments to the contrary I plan to increase
> HZ to 1000 on i386 this weekend. 

I don't object to increasing HZ, but will note that it results in a slight
increase in overhead relative to lower values on the same hadware.  It was
observed to me, however, that with modern CPUs, running HZ ten times
faster still results in a less overhead than on older processors with the
slower HZ, so... :-)

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Principal Research Scientist, McAfee Research


> 
> You can still define any HZ value you like in your kernel config file
> or even set it from the loader.
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk@FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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