From owner-freebsd-questions@FreeBSD.ORG Wed Jan 12 10:36:58 2005 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 40EE116A4CE for ; Wed, 12 Jan 2005 10:36:58 +0000 (GMT) Received: from kane.otenet.gr (kane.otenet.gr [195.170.0.27]) by mx1.FreeBSD.org (Postfix) with ESMTP id 50FBE43D45 for ; Wed, 12 Jan 2005 10:36:50 +0000 (GMT) (envelope-from keramida@ceid.upatras.gr) Received: from orion.daedalusnetworks.priv (aris.bedc.ondsl.gr [62.103.39.226])j0CAamSN010319; Wed, 12 Jan 2005 12:36:48 +0200 Received: from orion.daedalusnetworks.priv (orion [127.0.0.1]) j0CAaleH001382; Wed, 12 Jan 2005 12:36:47 +0200 (EET) (envelope-from keramida@ceid.upatras.gr) Received: (from keramida@localhost)j0CAalK9001381; Wed, 12 Jan 2005 12:36:47 +0200 (EET) (envelope-from keramida@ceid.upatras.gr) Date: Wed, 12 Jan 2005 12:36:47 +0200 From: Giorgos Keramidas To: Timothy Luoma Message-ID: <20050112103647.GA967@orion.daedalusnetworks.priv> References: <9094-SnapperMsgD246FC56BE0A255B@68.243.126.247> <20050112014359.GA3722@gothmog.gr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: cc: freebsd-questions@freebsd.org Subject: Re: Hyperthreading hurts 5.3? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 12 Jan 2005 10:36:58 -0000 On 2005-01-11 23:52, Timothy Luoma wrote: >On Jan 11, 2005, at 8:43 PM, Giorgos Keramidas wrote: >>On 2005-01-11 19:52, "Timothy J. Luoma" wrote: >>> >>> summary: should I disable hypertheading in the BIOS when running 5.3? >>> [...] >>> If YES, I wasn't clear if people meant "disable in BIOS" or just some >>> configuration setting in a *.conf file. >> >> FWIW, that should be enough, as far as FreeBSD is concerned. > > sorry to be dense, but which should be enough, BIOS or conf file? Oh, sorry about that. I must have beel sleepy when I replied and missed that there were two questions there. I meant that disabling HT from the BIOS setup should be enough for FreeBSD too. > is the default to use or not use hyperthreading in the kernel/conf? AFAICT from reading /usr/src/sys/i386/i386/mp_machdep.c, hyper-threading support is always enabled in FreeBSD if it is also enabled in the BIOS. The mp_topology() function contains, among other stuff: 222 void 223 mp_topology(void) 224 { 225 struct cpu_group *group; 226 int logical_cpus; 227 int apic_id; 228 int groups; 229 int cpu; 230 231 /* Build the smp_topology map. */ 232 /* Nothing to do if there is no HTT support. */ 233 if ((cpu_feature & CPUID_HTT) == 0) 234 return; 235 logical_cpus = (cpu_procinfo & CPUID_HTT_CORES) >> 16; 236 if (logical_cpus <= 1) 237 return;