From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stratos Karafotis Subject: Re: [PATCH 2/2] cpufreq: ondemand: Eliminate the deadband effect Date: Fri, 11 Jul 2014 22:37:01 +0300 Message-ID: <53C03CDD.5020701@semaphore.gr> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20140711183414.GA18951@amd.pavel.ucw.cz> Sender: linux-kernel-owner@vger.kernel.org To: Pavel Machek Cc: rjw@rjwysocki.net, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org On 11/07/2014 09:34 =CE=BC=CE=BC, Pavel Machek wrote: > On Fri 2014-07-11 20:29:57, Stratos Karafotis wrote: >> Hi Pavel! >> >> On 11/07/2014 07:57 =CE=BC=CE=BC, Pavel Machek wrote: >>> 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 lik= e >>> 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. >=20 > 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 leak= age current (thanks to Dirk Brandewie for this info). This simple test on a nearly idle system shows this: [root@albert cpufreq]# for CPUFREQ in /sys/devices/system/cpu/cpu*/cpuf= req/scaling_governor; do [ -f $CPUFREQ ] || continue; echo -n performan= ce > $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%c= 3 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 0.0= 0 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 0.0= 0 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 0.0= 0 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 0.0= 0 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 0.0= 1 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*/cpuf= req/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%c= 3 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 0.0= 1 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 0.0= 0 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 0.0= 0 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 0.0= 2 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 0.0= 0 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. This is the reason that the intel_pstate driver don't use 'performance' and try to request a low P state when there is no load. > (Can you try to modify your code and rerun for example the apache > test?) Yes, I can do the apache test if the above example is not enough. >>> So... should we do that, or do we need better benchmark? >> >> I'm sorry. I'm not sure I understood exactly what do you mean by "be= tter >> benchmark". >=20 > I believe that any increase of frequency in frequency will make the > benchmarks you qouted better (on i7). Actually, you can probably just > select performance governor...? Maybe in benchmarks where the CPU load is high. But definitely not, in = mp3 decoding and idle system test. The point is, as you mentioned, more tests and of course on other CPUs. Unfortunately, I can test only on i7 and krait as mentioned in changelo= g. I will happily run any test you would like for more info. Thanks, Stratos