From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752764AbZECGIR (ORCPT ); Sun, 3 May 2009 02:08:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751210AbZECGH6 (ORCPT ); Sun, 3 May 2009 02:07:58 -0400 Received: from gw1.cosmosbay.com ([212.99.114.194]:43351 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751019AbZECGH5 convert rfc822-to-8bit (ORCPT ); Sun, 3 May 2009 02:07:57 -0400 Message-ID: <49FD347F.6030306@cosmosbay.com> Date: Sun, 03 May 2009 08:06:55 +0200 From: Eric Dumazet User-Agent: Thunderbird 2.0.0.21 (Windows/20090302) MIME-Version: 1.0 To: Ingo Molnar CC: Christoph Lameter , linux kernel , Andi Kleen , David Miller , jesse.brandeburg@intel.com, netdev@vger.kernel.org, haoki@redhat.com, mchan@broadcom.com, davidel@xmailserver.org, Mike Galbraith , Peter Zijlstra Subject: Re: [BUG] perf_counter: change cpu frequencies References: <49F71B63.8010503@cosmosbay.com> <49F76174.6060009@cosmosbay.com> <49F767FD.2040205@cosmosbay.com> <49F76F6C.80005@cosmosbay.com> <49F77108.7060509@cosmosbay.com> <20090429091130.GA27857@elte.hu> <49F9821C.5010802@cosmosbay.com> <20090430115736.GA24349@elte.hu> <49F9B0F0.40306@cosmosbay.com> <49F9CCD0.2080005@cosmosbay.com> In-Reply-To: <49F9CCD0.2080005@cosmosbay.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [0.0.0.0]); Sun, 03 May 2009 08:07:01 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Eric Dumazet a écrit : > Eric Dumazet a écrit : > >> But if I use plain "perf stat -a sleep 10" >> it seems I get wrong values again (16 G cycles/sec) for all next perf sessions >> > > Well, I confirm all my cpus switched from 3GHz to 2GHz, after > > "perf stat -a sleep 10" > > (but "perf stat -e instructions -e cycles -a sleep 10" doesnt trigger this problem) > > Nothing logged, and /proc/cpuinfo stills reports 3 GHz frequencies > > # cat unit.c > main() { > int i; > for (i = 0 ; i < 10000000; i++) > getppid(); > } > # time ./unit > > real 0m0.818s > user 0m0.289s > sys 0m0.529s > # perf stat -a sleep 10 2>/dev/null > # time ./unit > > real 0m1.122s > user 0m0.482s > sys 0m0.640s > > # tail -n 27 /proc/cpuinfo > processor : 7 > vendor_id : GenuineIntel > cpu family : 6 > model : 23 > model name : Intel(R) Xeon(R) CPU E5450 @ 3.00GHz > stepping : 6 > cpu MHz : 3000.102 > cache size : 6144 KB > physical id : 1 > siblings : 1 > core id : 3 > cpu cores : 4 > apicid : 7 > initial apicid : 7 > fdiv_bug : no > hlt_bug : no > f00f_bug : no > coma_bug : no > fpu : yes > fpu_exception : yes > cpuid level : 10 > wp : yes > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm constant_tsc arch_perfmon pebs bts pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 lahf_lm tpr_shadow vnmi flexpriority > bogomips : 6000.01 > clflush size : 64 > power management: > > # grep CPU_FREQ .config > # CONFIG_CPU_FREQ is not set > > > perf_counter seems promising, but still... needs some bug hunting :) > Update : Mike Galbraith suggested me to try various things, and finally, I discovered this frequency change was probably a BIOS problem on my HP BL460c G1 System Options -> Power regulator for Proliant [*] HP Dynamic Power Savings Mode [ ] HP Static Low Power Mode [ ] HP Static High Performance Mode [ ] OS Control Mode I switched it to 'OS Control Mode' Then acpi-cpufreq could load, and no more frequencies changes on a "perf -a sleep 10" session, using or not cpufreq. (Supported cpufreq speeds on these cpus : 1999 & 2999 MHz) So it was a BIOS issue # perf stat -a sleep 10 Performance counter stats for 'sleep': 80005.418223 task clock ticks (msecs) 80266 context switches (events) 3 CPU migrations (events) 486 pagefaults (events) 240013851624 CPU cycles (events) << good >> 239076501419 instructions (events) 679464 cache references (events) cache misses Wall-clock time elapsed: 10000.468808 msecs Thank you