Date: Thu, 7 May 2009 11:31:11 +0200 From: Olivier SMEDTS <olivier@gid0.org> To: barney_cordoba@yahoo.com Cc: pluknet <pluknet@gmail.com>, "Current@freebsd.org" <Current@freebsd.org> Subject: Re: Hypertherading Message-ID: <367b2c980905070231r37a94eack399f5afed742247f@mail.gmail.com> In-Reply-To: <758865.1091.qm@web63907.mail.re1.yahoo.com> References: <a31046fc0905061955u4a7b5755ifbcd7bd5641cd954@mail.gmail.com> <758865.1091.qm@web63907.mail.re1.yahoo.com>
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2009/5/7 Barney Cordoba <barney_cordoba@yahoo.com>: > > > > > --- 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? There can be some benefit if the scheduler is aware of the topoly of CPUs and Hyperthreading (shared cache). I don't know how SCHED_ULE handles this on -CURRENT. If it doesn't see any difference between CPU cores and "HT" cores, you should disable HT in BIOS. >> > >> >> 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 > > > > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" > -- Olivier Smedts _ ASCII ribbon campaign ( ) e-mail: olivier@gid0.org - against HTML email & vCards X www: http://www.gid0.org - against proprietary attachments / \ "Il y a seulement 10 sortes de gens dans le monde : ceux qui comprennent le binaire, et ceux qui ne le comprennent pas."
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