From owner-freebsd-current@FreeBSD.ORG Thu May 7 16:38:13 2009 Return-Path: Delivered-To: Current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 1C525106564A for ; Thu, 7 May 2009 16:38:13 +0000 (UTC) (envelope-from spawk@acm.poly.edu) Received: from acm.poly.edu (acm.poly.edu [128.238.9.200]) by mx1.freebsd.org (Postfix) with ESMTP id AD7698FC16 for ; Thu, 7 May 2009 16:38:12 +0000 (UTC) (envelope-from spawk@acm.poly.edu) Received: (qmail 88822 invoked from network); 7 May 2009 16:11:32 -0000 Received: from unknown (HELO ?192.168.0.2?) (spawk@69.123.45.64) by acm.poly.edu with AES256-SHA encrypted SMTP; 7 May 2009 16:11:32 -0000 Message-ID: <4A0307F7.6000403@acm.poly.edu> Date: Thu, 07 May 2009 12:10:31 -0400 From: Boris Kochergin User-Agent: Thunderbird 2.0.0.19 (X11/20090108) MIME-Version: 1.0 To: barney_cordoba@yahoo.com References: <418018.46727.qm@web63901.mail.re1.yahoo.com> In-Reply-To: <418018.46727.qm@web63901.mail.re1.yahoo.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: pluknet , "Current@freebsd.org" Subject: Re: Hypertherading X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 May 2009 16:38:13 -0000 Barney Cordoba wrote: > > > --- On Wed, 5/6/09, pluknet wrote: > > >> From: pluknet >> Subject: Re: Hypertherading >> To: "Barney Cordoba" >> Cc: "Current@freebsd.org" >> Date: Wednesday, May 6, 2009, 10:55 PM >> 2009/5/7 Barney Cordoba : >> >>> 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