linux-kernel - [PATCH] cpufreq: schedutil: Call sugov_update_next_freq() before check to fast_switch

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Message-Id: <20210224054232.1222-1-zbestahu@gmail.com>
Date:   Wed, 24 Feb 2021 13:42:32 +0800
From:   Yue Hu <zbestahu@...il.com>
To:     rjw@...ysocki.net, viresh.kumar@...aro.org, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        huyue2@...ong.com, zbestahu@....com
Subject: [PATCH] cpufreq: schedutil: Call sugov_update_next_freq() before check to fast_switch_enabled

From: Yue Hu <huyue2@...ong.com>

Note that sugov_update_next_freq() may return false, that means the
caller sugov_fast_switch() will do nothing except fast switch check.

Similarly, sugov_deferred_update() also has unnecessary operations
of raw_spin_{lock,unlock} in sugov_update_single_freq() for that case.

So, let's call sugov_update_next_freq() before the fast switch check
to avoid unnecessary behaviors above. Update the related interface
definitions accordingly.

Signed-off-by: Yue Hu <huyue2@...ong.com>
---
 kernel/sched/cpufreq_schedutil.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 41e498b..d23e5be 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -114,19 +114,13 @@ static bool sugov_update_next_freq(struct sugov_policy *sg_policy, u64 time,
 	return true;
 }
 
-static void sugov_fast_switch(struct sugov_policy *sg_policy, u64 time,
-			      unsigned int next_freq)
+static void sugov_fast_switch(struct sugov_policy *sg_policy, unsigned int next_freq)
 {
-	if (sugov_update_next_freq(sg_policy, time, next_freq))
-		cpufreq_driver_fast_switch(sg_policy->policy, next_freq);
+	cpufreq_driver_fast_switch(sg_policy->policy, next_freq);
 }
 
-static void sugov_deferred_update(struct sugov_policy *sg_policy, u64 time,
-				  unsigned int next_freq)
+static void sugov_deferred_update(struct sugov_policy *sg_policy)
 {
-	if (!sugov_update_next_freq(sg_policy, time, next_freq))
-		return;
-
 	if (!sg_policy->work_in_progress) {
 		sg_policy->work_in_progress = true;
 		irq_work_queue(&sg_policy->irq_work);
@@ -368,16 +362,19 @@ static void sugov_update_single_freq(struct update_util_data *hook, u64 time,
 		sg_policy->cached_raw_freq = cached_freq;
 	}
 
+	if (!sugov_update_next_freq(sg_policy, time, next_f))
+		return;
+
 	/*
 	 * This code runs under rq->lock for the target CPU, so it won't run
 	 * concurrently on two different CPUs for the same target and it is not
 	 * necessary to acquire the lock in the fast switch case.
 	 */
 	if (sg_policy->policy->fast_switch_enabled) {
-		sugov_fast_switch(sg_policy, time, next_f);
+		sugov_fast_switch(sg_policy, next_f);
 	} else {
 		raw_spin_lock(&sg_policy->update_lock);
-		sugov_deferred_update(sg_policy, time, next_f);
+		sugov_deferred_update(sg_policy);
 		raw_spin_unlock(&sg_policy->update_lock);
 	}
 }
@@ -456,12 +453,15 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
 	if (sugov_should_update_freq(sg_policy, time)) {
 		next_f = sugov_next_freq_shared(sg_cpu, time);
 
+		if (!sugov_update_next_freq(sg_policy, time, next_f))
+			goto unlock;
+
 		if (sg_policy->policy->fast_switch_enabled)
-			sugov_fast_switch(sg_policy, time, next_f);
+			sugov_fast_switch(sg_policy, next_f);
 		else
-			sugov_deferred_update(sg_policy, time, next_f);
+			sugov_deferred_update(sg_policy);
 	}
-
+unlock:
 	raw_spin_unlock(&sg_policy->update_lock);
 }
 
-- 
1.9.1