linux-kernel - [PATCH] cpufreq: schedutil: Don't skip freq update when limits change

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Message-Id: <8091ef83f264feb2feaa827fbeefe08348bcd05d.1563778071.git.viresh.kumar@linaro.org>
Date:   Mon, 22 Jul 2019 12:21:57 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rafael Wysocki <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        joel@...lfernandes.org, dsmythies@...us.net,
        "v4 . 18+" <stable@...r.kernel.org>,
        Doug Smythies <doug.smythies@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] cpufreq: schedutil: Don't skip freq update when limits change

To avoid reducing the frequency of a CPU prematurely, we skip reducing
the frequency if the CPU had been busy recently.

This should not be done when the limits of the policy are changed, for
example due to thermal throttling. We should always get the frequency
within limits as soon as possible.

Fixes: ecd288429126 ("cpufreq: schedutil: Don't set next_freq to UINT_MAX")
Cc: v4.18+ <stable@...r.kernel.org> # v4.18+
Reported-by: Doug Smythies <doug.smythies@...il.com>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
@Doug: Please try this patch, it must fix the issue you reported.

 kernel/sched/cpufreq_schedutil.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 636ca6f88c8e..b53c4f02b0f1 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -447,7 +447,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
 	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
 	unsigned long util, max;
 	unsigned int next_f;
-	bool busy;
+	bool busy = false;
 
 	sugov_iowait_boost(sg_cpu, time, flags);
 	sg_cpu->last_update = time;
@@ -457,7 +457,9 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
 	if (!sugov_should_update_freq(sg_policy, time))
 		return;
 
-	busy = sugov_cpu_is_busy(sg_cpu);
+	/* Limits may have changed, don't skip frequency update */
+	if (!sg_policy->need_freq_update)
+		busy = sugov_cpu_is_busy(sg_cpu);
 
 	util = sugov_get_util(sg_cpu);
 	max = sg_cpu->max;
-- 
2.21.0.rc0.269.g1a574e7a288b