sched/fair: Do not call cpufreq hook unless util changed

There's no reason to call the cpufreq hook if the root cfs_rq
utilization has not been modified.

Signed-off-by: Steve Muckle <smuckle@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <Juri.Lelli@arm.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: http://lkml.kernel.org/r/1458606068-7476-2-git-send-email-smuckle@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6df80d47a52500c24312e2eaec30540bb7c33baa..81552819444c3aae6a6da3291268c1785a19cb0a 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2879,20 +2879,21 @@ static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
 {
        struct sched_avg *sa = &cfs_rq->avg;
        struct rq *rq = rq_of(cfs_rq);
-       int decayed, removed = 0;
+       int decayed, removed_load = 0, removed_util = 0;
        int cpu = cpu_of(rq);
 
        if (atomic_long_read(&cfs_rq->removed_load_avg)) {
                s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
                sa->load_avg = max_t(long, sa->load_avg - r, 0);
                sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
-               removed = 1;
+               removed_load = 1;
        }
 
        if (atomic_long_read(&cfs_rq->removed_util_avg)) {
                long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
                sa->util_avg = max_t(long, sa->util_avg - r, 0);
                sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
+               removed_util = 1;
        }
 
        decayed = __update_load_avg(now, cpu, sa,
@@ -2903,7 +2904,8 @@ static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
        cfs_rq->load_last_update_time_copy = sa->last_update_time;
 #endif
 
-       if (cpu == smp_processor_id() && &rq->cfs == cfs_rq) {
+       if (cpu == smp_processor_id() && &rq->cfs == cfs_rq &&
+           (decayed || removed_util)) {
                unsigned long max = rq->cpu_capacity_orig;
 
                /*
@@ -2926,7 +2928,7 @@ static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
                                    min(sa->util_avg, max), max);
        }
 
-       return decayed || removed;
+       return decayed || removed_load;
 }
 
 /* Update task and its cfs_rq load average */