From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] CPU frequency display in /proc/cpuinfo Date: Mon, 05 Dec 2005 18:29:02 +0200 Message-ID: <43946ACE.9040405@argo.co.il> References: <20051202181927.GD9766@wotan.suse.de> <20051202104320.A5234@unix-os.sc.intel.com> <20051204164335.GB32492@isilmar.linta.de> <20051204183239.GE14247@wotan.suse.de> <1133725767.19768.12.camel@mindpipe> <20051205011611.GA12664@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20051205011611.GA12664@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: cpufreq-bounces@lists.linux.org.uk Errors-To: cpufreq-bounces+glkc-cpufreq=gmane.org+glkc-cpufreq=gmane.org@lists.linux.org.uk Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Dave Jones Cc: Andrew Morton , Andi Kleen , linux-kernel , Lee Revell , cpufreq Dave Jones wrote: >I can't think of a single valid reason why a program would want >to know the MHz rating of a CPU. Given that it's a) approximate, >b) subject to change due to power management, c) completely nonsensical >across CPU vendors, and d) only one of many variables regarding CPU >performance, any program that bases any decision on the values found >by parsing that field of /proc/cpuinfo is utterly broken beyond belief. > > Sometimes you need extremely low overhead time measurements, which need not be too accurate. One way to do this is to dump rdtsc measurements into some array, and later scale it using the cpu frequency. I've done exactly this. The processes were pinned to their processors, and there was no frequency scaling in effect. It worked very well.