[PATCH 1/3] sched/fair: skip idle cfs_rq

[Vincent Guittot]

Don't waste time checking whether an idle cfs_rq could be the busiest
queue. Furthermore, this can end up selecting a cfs_rq with a high load
but being idle in case of migrate_load.

Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
---
 kernel/sched/fair.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 04a3ce20da67..5428b8723e61 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9389,8 +9389,11 @@ static struct rq *find_busiest_queue(struct lb_env *env,
                if (rt > env->fbq_type)
                        continue;
 
-               capacity = capacity_of(i);
                nr_running = rq->cfs.h_nr_running;
+               if (!nr_running)
+                       continue;
+
+               capacity = capacity_of(i);
 
                /*
                 * For ASYM_CPUCAPACITY domains, don't pick a CPU that could
-- 
2.17.1