From owner-freebsd-questions@FreeBSD.ORG Tue Sep 20 21:28:21 2011 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id BF457106564A for ; Tue, 20 Sep 2011 21:28:21 +0000 (UTC) (envelope-from richard@blueapex.co.uk) Received: from moutng.kundenserver.de (moutng.kundenserver.de [212.227.17.8]) by mx1.freebsd.org (Postfix) with ESMTP id 4FFBE8FC1A for ; Tue, 20 Sep 2011 21:28:21 +0000 (UTC) Received: from [10.66.2.54] (zen-gw.ch.dishpower.net [82.68.0.22]) by mrelayeu.kundenserver.de (node=mreu4) with ESMTP (Nemesis) id 0MH9wU-1QtWvh2xQA-00Dmje; Tue, 20 Sep 2011 23:28:20 +0200 Message-ID: <4E790572.10602@blueapex.co.uk> Date: Tue, 20 Sep 2011 22:28:18 +0100 From: Richard Collyer User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-GB; rv:1.9.2.22) Gecko/20110902 Lightning/1.0b2 Thunderbird/3.1.14 MIME-Version: 1.0 To: freebsd-questions@freebsd.org References: <1316550882.13474.YahooMailClassic@web121217.mail.ne1.yahoo.com> In-Reply-To: <1316550882.13474.YahooMailClassic@web121217.mail.ne1.yahoo.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V02:K0:0z2k5mVN/1oyNyiT43N+5g4ExR95M4/JD3PmvKMhrjT stG92abV3psoNc/kSz3/MndwHbM5QsTVoq+vZvmbWjucViSla7 SRRlHXDcsNty9aOiwIDqb0yrBH4kY3+e4/V0Egl3HJusJVBErQ u4aoW5WkAR1HxPVMvmWoLbnq9U2HmtuJHU5PYTxqgMLTt6yEtU cKNTYYKfUtOSIKYs8vxFtjbtfRPOlCKpRLjmuuU4H8Pc+l2xjr 0dmcIb+33cgCn26Oaf7lbt13oc0d5HFpzmHyVRqvBozG5zzNEt 8LCNkMLfDwN9s/fRr1olhs7HYfsHyGlQjK/witQIE1AWCPu83M UfwlhIBfHtjDouf/aqws= Subject: Re: How can I disable hyperthreads, but NOT smp ? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Sep 2011 21:28:21 -0000 On 20/09/2011 21:34, Jason Usher wrote: > FreeBSD 6.4-RELEASE system with two physical CPUs, each of which are HT capable. From dmesg: > > cpu0 (BSP): APIC ID: 0 > cpu1 (AP): APIC ID: 1 > cpu2 (AP): APIC ID: 6 > cpu3 (AP): APIC ID: 7 > > I also see this: > > machdep.hyperthreading_allowed: 0 > > The problem is, I have reason to believe that my workload benefits greatly from SMP, but is not playing nicely with hyperthreading. That is, it is trying to farm out 4 things at a time to a cpu setup that really is only able to do two things at a time. > > How can I disable HT completely, but still retain ALL the benefits of SMP ? > > Thanks. It's usually a setting in the BIOS to disable Hyperthreading then reconfigure the kernel to only use 2 cores (which it might do automatically). Hyperthreading is outside the world of FreeBSD. As far as it knows there is still 4 "logical processors". Disabling hyperthreading it should see 2 LPs. Richard -- Richard Collyer Blue Apex Ltd 07900 997 380 Registered as a company in England and Wales (Reg Number: 05982514). Registered Address: 42 King Richards Hill, Earl Shilton, Leicester, LE9 7EY __________ Information from ESET NOD32 Antivirus, version of virus signature database 6480 (20110920) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com