[PATCH 5/6] cpufreq: schedutil: avoid utilisation update when not necessary

Patrick Bellasi
2017-03-02T15:48:37Z

Under certain conditions (i.e. CPU entering idle and current task being
the sugov thread) we can skip a frequency update.
Thus, let's postpone the collection of the FAIR utilisation when really
needed.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
---
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 44bff37..c8ed645 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -296,8 +296,6 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
unsigned int next_f;
bool rt_mode;

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

/* CPU is entering IDLE, reset flags without triggering an update */
@@ -323,6 +321,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
else
sg_cpu->flags = flags;

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

--
2.7.4