Date: Thu, 12 Apr 2007 15:24:08 -0700 From: Maxim Sobolev <sobomax@FreeBSD.org> To: Julian Elischer <julian@elischer.org> Cc: Ivan Voras <ivoras@fer.hr>, Randall Stewart <rrs@cisco.com>, freebsd-current@FreeBSD.org, Robert Watson <rwatson@FreeBSD.org>, Janardhan Iyengar <iyengar@conncoll.edu>, =?ISO-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no>, Brad Penoff <penoff@cs.ubc.ca> Subject: Re: CPU utilization Message-ID: <461EB188.3070303@FreeBSD.org> In-Reply-To: <461E74DA.3020402@elischer.org> References: <461E0078.3050001@cisco.com> <evl00c$89j$1@sea.gmane.org> <461E092B.4080001@cisco.com> <86d529zxci.fsf@dwp.des.no> <20070412153930.A99718@fledge.watson.org> <461E74DA.3020402@elischer.org>
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Julian Elischer wrote: > Robert Watson wrote: >> >> On Thu, 12 Apr 2007, Dag-Erling Smørgrav wrote: >> >>> Randall Stewart <rrs@cisco.com> writes: >>>> machdep.hyperthreading_allowed: 0 >>> >>> Note that enabling hyperthreading is more likely to harm performance >>> than to help it. You should just disable it in the BIOS, and run a >>> UP kernel. >> >> Historically this has been true, but some more recent results I've >> seen suggest that both hyperthreading hardware has improved, and the >> efficiency of our SMP implementation and scheduler has lead to it >> being more effective used. I would reevaluate this on more modern >> hardware and using a more recent kernel before assuming this remains >> true for your application. > > In addition to this, to answer the original question, I remember a > commit so that if you disable a cpu (or HT cpu) it doesn't get counted > in the CPU % so if you have 2 cpus and disable one hten prior to that > commit it was not possible to get > 50% busy but after that commit > you could get 100% "of the available CPUs". That fix is not (I believe) > in 6.2. That's correct. The fix went in after RELENG_6_2 has been branched. -Maxim
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