Date: Wed, 23 Feb 2005 08:23:02 -0800 From: John Pettitt <jpp@cloudview.com> To: cpghost@cordula.ws Cc: Robert Watson <rwatson@FreeBSD.org> Subject: Re: HZ=1000 on slow CPUs considered harmful? Message-ID: <421CADE6.2050205@cloudview.com> In-Reply-To: <20050222214821.GA66879@epia2.farid-hajji.net> References: <20050222193858.1C18C5D07@ptavv.es.net> <Pine.NEB.3.96L.1050222195429.68237B-100000@fledge.watson.org> <20050222214821.GA66879@epia2.farid-hajji.net>
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cpghost@cordula.ws wrote: >On Tue, Feb 22, 2005 at 07:56:03PM +0000, Robert Watson wrote: > > >>In 6-CURRENT, HZ is 1000 for amd64, i386, and ia64, but 100 for other >>platforms (i.e., ppc, arm, and alpha). I'm not opposed to merging the HZ >>change to RELENG_5 at some point, but given that occasional nits, such as >>the TCP nit, are turning up, I think it's worth waiting until after 5.4. >> >> > >Wouldn't that be a problem for slow CPUs like VIA C3 (EPIA) or GEODE >(Soekris)? For fast CPUs, it's not that much overhead, but for slow >CPUs? > >Can HZ remain user-configurable? > > > HZ=1000 has causes a lot of problems for Linux boxes where the system no longer keeps accurate time because of lost clock interrupts under high load (video playback seem to be the favorite) - see the ntp lists for extensive discussion. Is this change really worth the hassle? John
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