Date: Thu, 04 Nov 2004 17:36:53 +0100 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Scott Long <scottl@freebsd.org> Cc: arch@freebsd.org Subject: Re: HEADSUP: HZ=1000 by default on i386 Message-ID: <48657.1099586213@critter.freebsd.dk> In-Reply-To: Your message of "Thu, 04 Nov 2004 09:36:02 MST." <418A5A72.6020700@freebsd.org>
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In message <418A5A72.6020700@freebsd.org>, Scott Long writes: >>> 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? I only tested on i386, but any platform would suffer from this kind of syncronism/syntonism. -- 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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