Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761864AbYFKPhH (ORCPT ); Wed, 11 Jun 2008 11:37:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761661AbYFKPgv (ORCPT ); Wed, 11 Jun 2008 11:36:51 -0400 Received: from casper.infradead.org ([85.118.1.10]:58695 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761649AbYFKPgu (ORCPT ); Wed, 11 Jun 2008 11:36:50 -0400 Date: Wed, 11 Jun 2008 08:36:44 -0700 From: Arjan van de Ven To: "linux-os (Dick Johnson)" Cc: "Jan Engelhardt" , "Kok, Auke" , "solsTiCe d'Hiver" , Subject: Re: PROBLEM: no cpu MHz in /proc/cpuinfo on 2.6.25.4-rt6 Message-ID: <20080611083644.32afc823@infradead.org> In-Reply-To: References: <200806102152.23286.solstice.dhiver@gmail.com> <20080610131314.5f7069e6@infradead.org> <484EE71A.40002@intel.com> <20080611063639.5e1eea5b@infradead.org> <20080611065816.6cff290d@infradead.org> 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: 1306 Lines: 39 On Wed, 11 Jun 2008 10:14:50 -0400 "linux-os (Dick Johnson)" wrote: > > I use CPU frequency to scale the output of rdtsc when timing > routines being optimized. Ok this is broken in various really bad ways. 1) CPU frequency is very fluctuating, it changes in principle every millisecond or more 2) the rdtsc "frequency" is conceptually unrelated to cpu frequency. In fact, you'll be hard-pressed to buy a system today where this relationship works.... > If CPU frequency goes away, I'll > have to add calibration routines to a lot of code. I don't > think one should just dispose of something that has been > useful for many years because they don't understand its > utility. clearly you don't understand it either ;-) I'm not arguing for removing it, at all. I'm just arguing that any user of it (being human or program) has some problems in how they use the data. -- 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/