HEADSUP: HZ=1000 by default on i386
phk at phk.freebsd.dk
Thu Nov 4 08:32:13 PST 2004
In message <xzp7jp1wpli.fsf at dwp.des.no>, =?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?= writes:
>Poul-Henning Kamp <phk at 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
> 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 Kamp | UNIX since Zilog Zeus 3.20
phk at 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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