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Date: Thu, 04 Nov 2004 09:36:02 -0700
From: Scott Long <scottl@freebsd.org>
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To: Poul-Henning Kamp <phk@phk.freebsd.dk>
References: <48555.1099585930@critter.freebsd.dk>
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cc: =?ISO-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no>
cc: arch@freebsd.org
Subject: Re: HEADSUP: HZ=1000 by default on i386
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Poul-Henning Kamp wrote:
> In message <xzp7jp1wpli.fsf@dwp.des.no>, =?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?= writes:
> 
>>Poul-Henning Kamp <phk@phk.freebsd.dk> writes:
>>
>>>So pending any really good arguments to the contrary I plan to increase
>>>HZ to 1000 on i386 this weekend.
>>
>>two good arguments:
>>
>> 1) I'm already working on this, and you know it, since I asked you
>>    about it in Karlsruhe.
> 
> 
> Ahh, sorry, I got the impression that you were not going to do it on
> your own.
> 
> 
>> 2) 1000 is not a good choice, because we can't approximate it well
>>    with the 8254.  1268 is better, 1381 is even better, 1903 is the
>>    best we can do between 1000 and 2000, 2299 is the best we can do
>>    between 1000 and 5000.
> 
> 
> I played with it here and found that 1000 actually works better than 941.
> (1193182 / 941 ~= 1268) because the 941 gives a slow beat against 1Hz.
> 
> It is actually preferable to have a fast beat (jitter) than a slow
> beat (wander), particularly for people doing benchmarks.
> 
> Poul-Henning
> 

What timing hardware is used on amd64?  Would it suffer there too?

Scott