From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932976AbWL0Pxa (ORCPT ); Wed, 27 Dec 2006 10:53:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932978AbWL0Pxa (ORCPT ); Wed, 27 Dec 2006 10:53:30 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:36992 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932976AbWL0Px3 (ORCPT ); Wed, 27 Dec 2006 10:53:29 -0500 Subject: Re: How to detect multi-core and/or HT-enabled CPUs in 2.4.x and 2.6.x kernels From: Arjan van de Ven Reply-To: arjan@infradead.org To: knobi@knobisoft.de Cc: Gleb Natapov , linux-kernel@vger.kernel.org In-Reply-To: <20061227154158.54796.qmail@web32608.mail.mud.yahoo.com> References: <20061227154158.54796.qmail@web32608.mail.mud.yahoo.com> Content-Type: text/plain Organization: Intel International BV Date: Wed, 27 Dec 2006 16:53:26 +0100 Message-Id: <1167234806.3281.3966.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.8.2.1 (2.8.2.1-2.fc6) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > this is a real interesting question. Ganglia is coming [originally] > from the HPC side of computing. At least in the past HT as implemented > on XEONs did help a lot. Running two CPU+memory-bandwith intensive > processes on the same physical CPU would at best result in a 50/50 > performance split. So, knowing how many "real" CPUs are in a system is > interesting to us. but this 50/50 split is most likely because of either a cache or a bandwidth bottleneck, at which point "HT" is the wrong measure. (also if you go to things like SUN's Niagara CPU then it's even more clear that SMT isn't the right measure for performance capability) -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org