Date: Thu, 04 Nov 2004 17:32:10 +0100 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: des@des.no (=?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?=) Cc: arch@freebsd.org Subject: Re: HEADSUP: HZ=1000 by default on i386 Message-ID: <48555.1099585930@critter.freebsd.dk> In-Reply-To: Your message of "Thu, 04 Nov 2004 17:23:05 %2B0100." <xzp7jp1wpli.fsf@dwp.des.no>
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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 -- 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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