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Date:      Thu, 04 Jun 1998 14:03:59 -0400
From:      Mark Handley <mjh@east.isi.edu>
To:        Jim Lowe <james@miller.cs.uwm.edu>
Cc:        multimedia@FreeBSD.ORG
Subject:   Re: Tick, tock, I need a fast clock... 
Message-ID:  <3710.896983439@north.lcs.mit.edu>
In-Reply-To: Your message of "Thu, 04 Jun 1998 11:28:49 CDT." <199806041628.LAA02532@miller.cs.uwm.edu> 

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>Are there any timers available to applications in FreeBSD faster than
>10ms?  If not, is there a simple way to increase the interval timers
>minimal time to something like .1ms without adversely effecting system
>performance?

I has the same requirement earlier this week.  You can change the
value of HZ in /usr/src/sys/conf/param.c from the default value of 100
to something larger and rebuild.  My system is currently running with
this set to 1000, which allows interval timers using select of around
2ms (why isn't it 1ms??).  The system seems to run fine, but the
values measured for per-process CPU utilization by top (and presumably
other utilities) are low by an order of magnitude.  Presumably this is
a bug in some of the kernel stats code.

It does seem somewhat rediculous that HZ is still set to 100 by
default in these days of 400MHz processors.

Cheers,
	Mark

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