linux-kernel - Re: [PATCH 1/2] cpufreq: schedutil: Fix superfluous updates caused by need_freq

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Message-ID: <CAB8ipk_Ayqmh=Ch2aH2c+i-q+qdiQ317VBH1kOHYN=R9dt6LOw@mail.gmail.com>
Date: Wed, 9 Apr 2025 19:48:05 +0800
From: Xuewen Yan <xuewen.yan94@...il.com>
To: Stephan Gerhold <stephan.gerhold@...aro.org>
Cc: Sultan Alsawaf <sultan@...neltoast.com>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Viresh Kumar <viresh.kumar@...aro.org>, Ingo Molnar <mingo@...hat.com>, 
	Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
	Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, regressions@...ts.linux.dev, 
	Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH 1/2] cpufreq: schedutil: Fix superfluous updates caused by need_freq_update

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;