Date: Sun, 27 Apr 2003 23:50:04 +0200 From: Jesper Skriver <jesper@FreeBSD.org> To: Peter Wood <peter@alastria.net> Cc: freebsd-smp@freebsd.org Subject: Re: machdep.cpu_idle_hlt on a Dual AMD 2000+ MP Message-ID: <20030427215004.GA98202@FreeBSD.org> In-Reply-To: <af8oav4h43rd549afuusneuo6qle7vjrnm@4ax.com> References: <af8oav4h43rd549afuusneuo6qle7vjrnm@4ax.com>
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On Sun, Apr 27, 2003 at 07:35:39PM +0100, Peter Wood wrote: > Afternoon, > > I was reading all the threads regarding hyperthreading, and descovered that > machdep.cpu_idle_hlt is set to 0 by default on SMP machines and 1 on > uniprocessor machines. > > I've change it to 1 on my dual machine, and so far it appears stable. I have > noticed that the CPU tempratures appear to be lower now, possibly a > coincidence as the servers load may have been changing. Should I expect it to > be lower? Yes, you should expect the temperature and power usage to be lower. > Also should I expect to see any performance loss, or instability? Does anyone > know the original reason for setting the defaults this way? There is a slight performance loss on SMP systems, this is the reason for the default. /Jesper -- Jesper Skriver, jesper(at)skriver(dot)dk - CCIE #5456 One Unix to rule them all, One Resolver to find them, One IP to bring them all and in the zone to bind them.
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