Date: Thu, 07 May 2009 12:10:31 -0400 From: Boris Kochergin <spawk@acm.poly.edu> To: barney_cordoba@yahoo.com Cc: pluknet <pluknet@gmail.com>, "Current@freebsd.org" <Current@freebsd.org> Subject: Re: Hypertherading Message-ID: <4A0307F7.6000403@acm.poly.edu> In-Reply-To: <418018.46727.qm@web63901.mail.re1.yahoo.com> References: <418018.46727.qm@web63901.mail.re1.yahoo.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Barney Cordoba wrote: > > > --- 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 >> >> >> -- >> wbr, >> pluknet >> > > I assume you mean hyperthreading-allowed? > > I set > > sysctl -a | grep hyper > > machdep.hyperthreading_allowed: 0 > > > but it still launches 16 cpus. Is that expected? It doesn't seem correct. > > 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" > If I recall correctly, that sysctl only prevents processes from being scheduled on the "virtual" hyper-threaded CPUs, and does not affect their discovery by the kernel. -Boris
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4A0307F7.6000403>