Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935249AbdIYNzQ (ORCPT ); Mon, 25 Sep 2017 09:55:16 -0400 Received: from foss.arm.com ([217.140.101.70]:52044 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934254AbdIYNzP (ORCPT ); Mon, 25 Sep 2017 09:55:15 -0400 Date: Mon, 25 Sep 2017 14:55:07 +0100 From: Patrick Bellasi To: Leo Yan Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, Dietmar Eggemann , Morten Rasmussen , Chris Redpath , Joel Fernandes , Vincent Guittot Subject: Re: [PATCH 2/2] cpufreq: schedutil: consolidate capacity margin calculation Message-ID: <20170925135507.GA3621@e110439-lin> References: <1506121484-8260-1-git-send-email-leo.yan@linaro.org> <1506121484-8260-2-git-send-email-leo.yan@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1506121484-8260-2-git-send-email-leo.yan@linaro.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2848 Lines: 73 On 23-Sep 07:04, Leo Yan wrote: > Scheduler CFS class has variable 'capacity_margin' to calculate the > capacity margin, and schedutil governor also needs to compensate the > same margin for frequency tipping point. Below are formulas used in > CFS class and schedutil governor separately: > > CFS: U` = U * capacity_margin / 1024 = U * 1.25 > Schedutil: U` = U + U >> 2 = U + U * 0.25 = U * 1.25 > > This patch consolidates the capacity margin calculation so let > schedutil to use same formula with CFS class. As result this can avoid > the mismatch issue between schedutil and CFS class after change > 'capacity_margin' to other values. > > Cc: Dietmar Eggemann > Cc: Morten Rasmussen > Cc: Chris Redpath > Cc: Joel Fernandes > Cc: Vincent Guittot > Signed-off-by: Leo Yan > --- > kernel/sched/cpufreq_schedutil.c | 5 +++-- > kernel/sched/sched.h | 1 + > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > index 9209d83..067abbe 100644 > --- a/kernel/sched/cpufreq_schedutil.c > +++ b/kernel/sched/cpufreq_schedutil.c > @@ -155,7 +155,8 @@ static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time, > * > * next_freq = C * curr_freq * util_raw / max > * > - * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8. > + * Take C = capacity_margin / 1024 = 1.25, so it's for the frequency tipping > + * point at (util / max) = 0.8. > * > * The lowest driver-supported frequency which is equal or greater than the raw > * next_freq (as calculated above) is returned, subject to policy min/max and > @@ -168,7 +169,7 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy, > unsigned int freq = arch_scale_freq_invariant() ? > policy->cpuinfo.max_freq : policy->cur; > > - freq = (freq + (freq >> 2)) * util / max; > + freq = (freq * capacity_margin / 1024) * util / max; The compiler should be smart enough but perhaps you can better use: freq *= (capacity_margin >> SCHED_CAPACITY_SHIFT)); freq *= util / max; > if (freq == sg_policy->cached_raw_freq && sg_policy->next_freq != UINT_MAX) > return sg_policy->next_freq; > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 14db76c..cf75bdc 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -52,6 +52,7 @@ struct cpuidle_state; > #define TASK_ON_RQ_MIGRATING 2 > > extern __read_mostly int scheduler_running; > +extern unsigned int capacity_margin __read_mostly; > > extern unsigned long calc_load_update; > extern atomic_long_t calc_load_tasks; > -- > 2.7.4 > -- #include Patrick Bellasi