From 170826dc7e7ccdcc57f4abf4cf3dc232d734fa71 Mon Sep 17 00:00:00 2001
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: Wed, 24 May 2017 10:59:55 +0530
Subject: [PATCH] sched/fair: Avoid checking cfs_rq->nr_running twice
References: bnc#1066110 Scheduler utilisation tracking
Patch-mainline: v4.14-rc1
Git-commit: 9674f5cad22a590c865a330ce333026b9f9c078b
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.kumar@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Link: http://lkml.kernel.org/r/000903ab3df3350943d3271c53615893a230dc95.1495603536.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
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 f0ddb7a7a683..4f93c7edb81e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6249,10 +6249,10 @@ 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;
@@ -6282,11 +6282,17 @@ 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);
@@ -6326,12 +6332,8 @@ 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 {