[PATCH 2/2] sched/fair: do not call cpufreq hook unless util changed

Steve Muckle
2016-03-22T00:21:19Z

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>
---
kernel/sched/fair.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d418deb04049..af58e826cffe 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2826,20 +2826,21 @@ 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,
@@ -2850,7 +2851,8 @@ 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;

/*
@@ -2873,7 +2875,7 @@ 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 */
--
2.4.10