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Wysocki" , Viresh Kumar , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, regressions@lists.linux.dev, Johan Hovold Subject: Re: [PATCH 1/2] cpufreq: schedutil: Fix superfluous updates caused by need_freq_update Message-ID: References: <20241212015734.41241-1-sultan@kerneltoast.com> <20241212015734.41241-2-sultan@kerneltoast.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Apr 09, 2025 at 07:48:05PM +0800, Xuewen Yan wrote: > Or can we modify it as follows? > > -->8-- > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > index 1a19d69b91ed..0e8d3b92ffe7 100644 > --- a/kernel/sched/cpufreq_schedutil.c > +++ b/kernel/sched/cpufreq_schedutil.c > @@ -83,7 +83,7 @@ static bool sugov_should_update_freq(struct > sugov_policy *sg_policy, u64 time) > > if (unlikely(sg_policy->limits_changed)) { > sg_policy->limits_changed = false; > - sg_policy->need_freq_update = > cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS); > + sg_policy->need_freq_update = true; > return true; > } > > @@ -95,11 +95,15 @@ static bool sugov_should_update_freq(struct > sugov_policy *sg_policy, u64 time) > static bool sugov_update_next_freq(struct sugov_policy *sg_policy, u64 time, > unsigned int next_freq) > { > - if (sg_policy->need_freq_update) > + if (sg_policy->need_freq_update) { > sg_policy->need_freq_update = false; > - else if (sg_policy->next_freq == next_freq) > - return false; > + if (cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS)) > + goto change; > + } > > + if (sg_policy->next_freq == next_freq) > + return false; > +change: > sg_policy->next_freq = next_freq; > sg_policy->last_freq_update_time = time; If CPUFREQ_NEED_UPDATE_LIMITS isn't specified, then there's no need to request a frequency switch from the driver when the current frequency is exactly the same as the next frequency. Sultan