Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751380AbaGTVv4 (ORCPT ); Sun, 20 Jul 2014 17:51:56 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:46645 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750835AbaGTVvy (ORCPT ); Sun, 20 Jul 2014 17:51:54 -0400 Date: Sun, 20 Jul 2014 23:51:51 +0200 From: Pavel Machek To: Stratos Karafotis Cc: rjw@rjwysocki.net, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] cpufreq: ondemand: Eliminate the deadband effect Message-ID: <20140720215151.GA7817@amd.pavel.ucw.cz> References: <1404147574-17422-1-git-send-email-stratosk@semaphore.gr> <1404147574-17422-3-git-send-email-stratosk@semaphore.gr> <20140711165710.GA18033@amd.pavel.ucw.cz> <53C01F15.2090702@semaphore.gr> <20140711183414.GA18951@amd.pavel.ucw.cz> <53C03CDD.5020701@semaphore.gr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53C03CDD.5020701@semaphore.gr> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! > >>>> Tested on Intel i7-3770 CPU @ 3.40GHz and on ARM quad core 1500MHz Krait > >>>> (Android smartphone). > >>>> Benchmarks on Intel i7 shows a performance improvement on low and medium > >>>> work loads with lower power consumption. Specifics: > >>>> > >>>> Phoronix Linux Kernel Compilation 3.1: > >>>> Time: -0.40%, energy: -0.07% > >>>> Phoronix Apache: > >>>> Time: -4.98%, energy: -2.35% > >>>> Phoronix FFMPEG: > >>>> Time: -6.29%, energy: -4.02% > >>> > >>> Hmm. Intel i7 should be race-to-idle machine. So basically rule like > >>> if (load > 0) go to max frequency else go to lowest frequency would do > >>> the right thing in your test, right? > >> > >> I don't think that "if (load > 0) go to max" will work even on i7. > >> For low load this will have impact on energy consumption. > > > > Are you sure? CPU frequency should not matter on idle CPU. > > Even on a totally idle CPU there will be a small impact because of leakage > current (thanks to Dirk Brandewie for this info). Are you sure? IIRC Intel cpus will automatically lower CPU frequency in deep C states.. > This simple test on a nearly idle system shows this: > > [root@albert cpufreq]# for CPUFREQ in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do [ -f $CPUFREQ ] || continue; echo -n performance > $CPUFREQ; done > [root@albert cpufreq]# /home/stratosk/kernels/linux-pm/tools/power/x86/turbostat/turbostat -J sleep 20 > Core CPU Avg_MHz %Busy Bzy_MHz TSC_MHz SMI CPU%c1 CPU%c3 CPU%c6 CPU%c7 CoreTmp PkgTmp Pkg%pc2 Pkg%pc3 Pkg%pc6 Pkg%pc7 Pkg_J Cor_J GFX_J time > - - 2 0.06 2712 3392 0 0.30 0.00 99.63 0.00 34 34 8.09 0.00 81.94 0.00 380.41 14.51 1.64 20.00 > 0 0 0 0.02 1891 3392 0 0.09 0.00 99.88 0.00 34 34 8.09 0.00 81.94 0.00 380.41 14.51 1.64 20.00 > 0 4 1 0.04 3006 3392 0 0.07 > 1 1 1 0.04 2501 3392 0 0.62 0.00 99.33 0.00 34 > 1 5 0 0.01 2346 3392 0 0.66 > 2 2 0 0.01 1996 3392 0 0.44 0.00 99.55 0.00 34 > 2 6 4 0.18 2278 3392 0 0.26 > 3 3 5 0.15 3449 3392 0 0.07 0.01 99.77 0.00 34 > 3 7 0 0.01 1839 3392 0 0.21 > 20.000899 sec > [root@albert cpufreq]# ^C > [root@albert cpufreq]# for CPUFREQ in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do [ -f $CPUFREQ ] || continue; echo -n ondemand > $CPUFREQ; done > [root@albert cpufreq]# /home/stratosk/kernels/linux-pm/tools/power/x86/turbostat/turbostat -J sleep 20 > Core CPU Avg_MHz %Busy Bzy_MHz TSC_MHz SMI CPU%c1 CPU%c3 CPU%c6 CPU%c7 CoreTmp PkgTmp Pkg%pc2 Pkg%pc3 Pkg%pc6 Pkg%pc7 Pkg_J Cor_J GFX_J time > - - 2 0.09 1693 3392 0 0.35 0.01 99.55 0.00 35 36 8.33 0.00 84.31 0.00 377.68 12.23 1.15 20.00 > 0 0 1 0.08 1603 3392 0 0.13 0.00 99.79 0.00 35 36 8.33 0.00 84.31 0.00 377.68 12.23 1.15 20.00 > 0 4 1 0.08 1646 3392 0 0.13 > 1 1 1 0.06 1647 3392 0 0.66 0.00 99.28 0.00 35 > 1 5 0 0.01 1611 3392 0 0.71 > 2 2 0 0.02 1617 3392 0 0.50 0.02 99.46 0.00 35 > 2 6 4 0.22 1764 3392 0 0.30 > 3 3 4 0.25 1701 3392 0 0.07 0.00 99.68 0.00 35 > 3 7 0 0.01 1602 3392 0 0.31 > 20.001580 sec > > > So, for low loads the impact will be higher. So it seems ondemand saves cca 1% of energy? Best regards, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/