[PATCH 4/6] sched: fair: Avoid checking cfs_rq->nr_running twice

[Viresh Kumar]

Rearrange pick_next_task_fair() a bit to avoid checking
cfs_rq->nr_running twice for the case where FAIR_GROUP_SCHED is enabled
and the previous task doesn't belong to the fair class.

Signed-off-by: Viresh Kumar <viresh.ku...@linaro.org>
---
 kernel/sched/fair.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fe03efd3880a..e519f6c03fe9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6267,10 +6267,10 @@ pick_next_task_fair(struct rq *rq, struct task_struct 
*prev, struct rq_flags *rf
        int new_tasks;
 
 again:
-#ifdef CONFIG_FAIR_GROUP_SCHED
        if (!cfs_rq->nr_running)
                goto idle;
 
+#ifdef CONFIG_FAIR_GROUP_SCHED
        if (prev->sched_class != &fair_sched_class)
                goto simple;
 
@@ -6300,11 +6300,17 @@ pick_next_task_fair(struct rq *rq, struct task_struct 
*prev, struct rq_flags *rf
                        /*
                         * This call to check_cfs_rq_runtime() will do the
                         * throttle and dequeue its entity in the parent(s).
-                        * Therefore the 'simple' nr_running test will indeed
+                        * Therefore the nr_running test will indeed
                         * be correct.
                         */
-                       if (unlikely(check_cfs_rq_runtime(cfs_rq)))
+                       if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
+                               cfs_rq = &rq->cfs;
+
+                               if (!cfs_rq->nr_running)
+                                       goto idle;
+
                                goto simple;
+                       }
                }
 
                se = pick_next_entity(cfs_rq, curr);
@@ -6344,12 +6350,8 @@ pick_next_task_fair(struct rq *rq, struct task_struct 
*prev, struct rq_flags *rf
 
        return p;
 simple:
-       cfs_rq = &rq->cfs;
 #endif
 
-       if (!cfs_rq->nr_running)
-               goto idle;
-
        put_prev_task(rq, prev);
 
        do {
-- 
2.13.0.70.g6367777092d9