Date: Thu, 12 Apr 2007 15:40:48 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?= <des@des.no> Cc: Randall Stewart <rrs@cisco.com>, freebsd-current@freebsd.org, Ivan Voras <ivoras@fer.hr>, Brad Penoff <penoff@cs.ubc.ca>, Janardhan Iyengar <iyengar@conncoll.edu> Subject: Re: CPU utilization Message-ID: <20070412153930.A99718@fledge.watson.org> In-Reply-To: <86d529zxci.fsf@dwp.des.no> References: <461E0078.3050001@cisco.com> <evl00c$89j$1@sea.gmane.org> <461E092B.4080001@cisco.com> <86d529zxci.fsf@dwp.des.no>
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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. Robert N M Watson Computer Laboratory University of Cambridge
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