Date: Thu, 7 May 2009 02:26:49 -0700 (PDT) From: Barney Cordoba <barney_cordoba@yahoo.com> To: pluknet <pluknet@gmail.com> Cc: "Current@freebsd.org" <Current@freebsd.org> Subject: Re: Hypertherading Message-ID: <758865.1091.qm@web63907.mail.re1.yahoo.com> In-Reply-To: <a31046fc0905061955u4a7b5755ifbcd7bd5641cd954@mail.gmail.com>
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--- On Wed, 5/6/09, pluknet <pluknet@gmail.com> wrote: > From: pluknet <pluknet@gmail.com> > Subject: Re: Hypertherading > To: "Barney Cordoba" <barney_cordoba@yahoo.com> > Cc: "Current@freebsd.org" <Current@freebsd.org> > Date: Wednesday, May 6, 2009, 10:55 PM > 2009/5/7 Barney Cordoba <barney_cordoba@yahoo.com>: > > > > I just got a shiny new nehalem box and it comes up > with 16 processors with dual quads installed. Is there any > benefit or should hyperthreading be disabled? > > > > Hi. There is a measurable win if hyperthreading is enabled > [1]. > You can switch it off via machdep.hyperthreading_enabled > loader tunable. > > [1] > http://lists.freebsd.org/pipermail/freebsd-stable/2009-January/047460.html > I wouldn't call varying the number of jobs a very good test of hyperthreading. I'd want to see the exact same test with hyperthreading enabled and disabled. Its pretty naive to assume that running 16 jobs causes them to all be run on a different cpu. Barney
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