Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756097AbYFKV25 (ORCPT ); Wed, 11 Jun 2008 17:28:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752700AbYFKV2t (ORCPT ); Wed, 11 Jun 2008 17:28:49 -0400 Received: from casper.infradead.org ([85.118.1.10]:37619 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752695AbYFKV2t (ORCPT ); Wed, 11 Jun 2008 17:28:49 -0400 Date: Wed, 11 Jun 2008 14:28:40 -0700 From: Arjan van de Ven To: markh@compro.net Cc: "linux-os (Dick Johnson)" , Jan Engelhardt , "Kok, Auke" , "solsTiCe d'Hiver" , linux-kernel@vger.kernel.org Subject: Re: PROBLEM: no cpu MHz in /proc/cpuinfo on 2.6.25.4-rt6 Message-ID: <20080611142840.47d65782@infradead.org> In-Reply-To: <48503EB9.6000606@compro.net> References: <200806102152.23286.solstice.dhiver@gmail.com> <20080610131314.5f7069e6@infradead.org> <484EE71A.40002@intel.com> <20080611063639.5e1eea5b@infradead.org> <20080611065816.6cff290d@infradead.org> <20080611083644.32afc823@infradead.org> <4850046C.4070602@compro.net> <20080611104446.3b0ce2d9@infradead.org> <48501159.4050908@compro.net> <48503792.50003@compro.net> <20080611135828.29f6a7d7@infradead.org> <48503EB9.6000606@compro.net> Organization: Intel X-Mailer: Claws Mail 3.3.1 (GTK+ 2.12.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1032 Lines: 29 On Wed, 11 Jun 2008 17:08:09 -0400 Mark Hounschell wrote: > > > > btw you also changed the problem from "what is the cpu frequency" to > > "how usable is rdtsc for time". My entire point was that these > > weren't related... > > > > > > If they are not the same how do you know at what rate the tsc is > counting. it's not ticking at the cpu frequency as general rule. For current cpus, your best bet is to calibrate against some external time source... it'll stay constant after that, unless you go to idle, then it may or may not stop (or both). For older cpus it'll change with frequency changes. -- If you want to reach me at my work email, use arjan@linux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/