Date: Thu, 04 Nov 2004 09:36:02 -0700 From: Scott Long <scottl@freebsd.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: arch@freebsd.org Subject: Re: HEADSUP: HZ=1000 by default on i386 Message-ID: <418A5A72.6020700@freebsd.org> In-Reply-To: <48555.1099585930@critter.freebsd.dk> References: <48555.1099585930@critter.freebsd.dk>
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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
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