linux-kernel - [PATCH v3 3/6] cpufreq: schedutil: update CFS util only if used

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Date:   Thu, 30 Nov 2017 11:47:20 +0000
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...roid.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: [PATCH v3 3/6] cpufreq: schedutil: update CFS util only if used

Currently the utilization of the FAIR class is collected before locking
the policy. Although that should not be a big issue for most cases, we
also don't really know how much latency there can be between the
utilization reading and its usage.

Let's get the FAIR utilization right before its usage to be better in
sync with the current status of a CPU.

Signed-off-by: Patrick Bellasi <patrick.bellasi@....com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Cc: linux-kernel@...r.kernel.org
Cc: linux-pm@...r.kernel.org

---
Changes from v2:
- rebased on v4.15-rc1

Change-Id: I9291a560bcad7db76894e3f0fcdb917511d0479e
---
 kernel/sched/cpufreq_schedutil.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 448f49de5335..40521d59630b 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -351,10 +351,9 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
 	unsigned int next_f;
 	bool rt_mode;

-	sugov_get_util(&util, &max, sg_cpu->cpu);
-
 	raw_spin_lock(&sg_policy->update_lock);

+	sugov_get_util(&util, &max, sg_cpu->cpu);
 	sg_cpu->util = util;
 	sg_cpu->max = max;

-- 
2.14.1