From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751887AbaEAVAo (ORCPT ); Thu, 1 May 2014 17:00:44 -0400 Received: from sema.semaphore.gr ([78.46.194.137]:46328 "EHLO sema.semaphore.gr" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750851AbaEAVAl (ORCPT ); Thu, 1 May 2014 17:00:41 -0400 Message-ID: <5362B5F5.1020706@semaphore.gr> Date: Fri, 02 May 2014 00:00:37 +0300 From: Stratos Karafotis User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: "Rafael J. Wysocki" , Viresh Kumar , Dirk Brandewie CC: "cpufreq@vger.kernel.org" , "linux-pm@vger.kernel.org" , LKML , dirk.brandewie@gmail.com Subject: [PATCH v2] cpufreq: intel_pstate: Change the calculation of next pstate Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently the driver calculates the next pstate proportional to core_busy factor, scaled by the ratio max_pstate / current_pstate. Using the scaled load (core_busy) to calculate the next pstate is not always correct, because there are cases that the load is independent from current pstate. For example, a tight 'for' loop through many sampling intervals will cause a load of 100% in every pstate. So, change the above method and calculate the next pstate with the assumption that the next pstate should not depend on the current pstate. The next pstate should only be directly proportional to measured load. Tested on Intel i7-3770 CPU @ 3.40GHz. Phoronix benchmark of Linux Kernel Compilation 3.1 test shows an increase ~1.5% in performance. Below the test results using turbostat (5 iterations): Without patch: Ph. avg Time Total time PkgWatt Total Energy 79.63 266.416 57.74 15382.85984 79.63 265.609 57.87 15370.79283 79.57 266.994 57.54 15362.83476 79.53 265.304 57.83 15342.53032 79.71 265.977 57.76 15362.83152 avg 79.61 266.06 57.74 15364.36985 With patch: Ph. avg Time Total time PkgWatt Total Energy 78.23 258.826 59.14 15306.96964 78.41 259.110 59.15 15326.35650 78.40 258.530 59.26 15320.48780 78.46 258.673 59.20 15313.44160 78.19 259.075 59.16 15326.87700 avg 78.34 258.842 59.18 15318.82650 The total test time reduced by ~2.6%, while the total energy consumption during a test iteration reduced by ~0.35% Signed-off-by: Stratos Karafotis --- Changes v1 -> v2 - Enhance change log as Rafael and Viresh suggested drivers/cpufreq/intel_pstate.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 0999673..8e309db 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -608,28 +608,27 @@ static inline void intel_pstate_set_sample_time(struct cpudata *cpu) mod_timer_pinned(&cpu->timer, jiffies + delay); } -static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu) +static inline int32_t intel_pstate_get_busy(struct cpudata *cpu) { - int32_t core_busy, max_pstate, current_pstate; + int32_t core_busy, max_pstate; core_busy = cpu->sample.core_pct_busy; max_pstate = int_tofp(cpu->pstate.max_pstate); - current_pstate = int_tofp(cpu->pstate.current_pstate); - core_busy = mul_fp(core_busy, div_fp(max_pstate, current_pstate)); + core_busy = mul_fp(core_busy, max_pstate); return FP_ROUNDUP(core_busy); } static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu) { - int32_t busy_scaled; + int32_t busy; struct _pid *pid; signed int ctl = 0; int steps; pid = &cpu->pid; - busy_scaled = intel_pstate_get_scaled_busy(cpu); + busy = intel_pstate_get_busy(cpu); - ctl = pid_calc(pid, busy_scaled); + ctl = pid_calc(pid, busy); steps = abs(ctl); @@ -651,7 +650,7 @@ static void intel_pstate_timer_func(unsigned long __data) intel_pstate_adjust_busy_pstate(cpu); trace_pstate_sample(fp_toint(sample->core_pct_busy), - fp_toint(intel_pstate_get_scaled_busy(cpu)), + fp_toint(intel_pstate_get_busy(cpu)), cpu->pstate.current_pstate, sample->mperf, sample->aperf, -- 1.9.0