From 9674f5cad22a590c865a330ce333026b9f9c078b Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Wed, 24 May 2017 10:59:55 +0530 Subject: [PATCH] sched/fair: Avoid checking cfs_rq->nr_running twice 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 Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Vincent Guittot Cc: linaro-kernel@lists.linaro.org Link: http://lkml.kernel.org/r/000903ab3df3350943d3271c53615893a230dc95.1495603536.git.viresh.kumar@linaro.org Signed-off-by: Ingo Molnar --- 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 27d425e..30fd196 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6187,10 +6187,10 @@ 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; @@ -6220,11 +6220,17 @@ again: /* * 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); @@ -6264,12 +6270,8 @@ again: return p; simple: - cfs_rq = &rq->cfs; #endif - if (!cfs_rq->nr_running) - goto idle; - put_prev_task(rq, prev); do { -- 2.7.4