Commit-ID: 2539fc82aa9b07d968cf9ba1ffeec3e0416ac721
Gitweb: https://git.kernel.org/tip/2539fc82aa9b07d968cf9ba1ffeec3e0416ac721
Author: Patrick Bellasi <[email protected]>
AuthorDate: Thu, 24 May 2018 15:10:23 +0100
Committer: Ingo Molnar <[email protected]>
CommitDate: Fri, 25 May 2018 08:04:56 +0200
sched/fair: Update util_est before updating schedutil
When a task is enqueued the estimated utilization of a CPU is updated
to better support the selection of the required frequency.
However, schedutil is (implicitly) updated by update_load_avg() which
always happens before util_est_{en,de}queue(), thus potentially
introducing a latency between estimated utilization updates and
frequency selections.
Let's update util_est at the beginning of enqueue_task_fair(),
which will ensure that all schedutil updates will see the most
updated estimated utilization value for a CPU.
Reported-by: Vincent Guittot <[email protected]>
Signed-off-by: Patrick Bellasi <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Acked-by: Viresh Kumar <[email protected]>
Acked-by: Vincent Guittot <[email protected]>
Cc: Dietmar Eggemann <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Morten Rasmussen <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rafael J . Wysocki <[email protected]>
Cc: Steve Muckle <[email protected]>
Fixes: 7f65ea42eb00 ("sched/fair: Add util_est on top of PELT")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched/fair.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 748cb054fefd..e497c05aab7f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5385,6 +5385,14 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p,
int flags)
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se;
+ /*
+ * The code below (indirectly) updates schedutil which looks at
+ * the cfs_rq utilization to select a frequency.
+ * Let's add the task's estimated utilization to the cfs_rq's
+ * estimated utilization, before we update schedutil.
+ */
+ util_est_enqueue(&rq->cfs, p);
+
/*
* If in_iowait is set, the code below may not trigger any cpufreq
* utilization updates, so do it here explicitly with the IOWAIT flag
@@ -5426,7 +5434,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p,
int flags)
if (!se)
add_nr_running(rq, 1);
- util_est_enqueue(&rq->cfs, p);
hrtick_update(rq);
}
