The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: 4892f51ad54ddff2883a60b6ad4323c1f632a9d6
Gitweb: https://git.kernel.org/tip/4892f51ad54ddff2883a60b6ad4323c1f632a9d6
Author: Quentin Perret <qperret@xxxxxxxxxxx>
AuthorDate: Fri, 20 Sep 2019 11:41:15 +02:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 25 Sep 2019 17:42:32 +02:00
sched/fair: Avoid redundant EAS calculation
The EAS wake-up path computes the system energy for several CPU
candidates: the CPU with maximum spare capacity in each performance
domain, and the prev_cpu. However, if prev_cpu also happens to be the
CPU with maximum spare capacity in its performance domain, the energy
calculation is still done twice, unnecessarily.
Add a condition to filter out this corner case before doing the energy
calculation.
Reported-by: Pavan Kondeti <pkondeti@xxxxxxxxxxxxxx>
Signed-off-by: Quentin Perret <qperret@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: dietmar.eggemann@xxxxxxx
Cc: juri.lelli@xxxxxxxxxx
Cc: morten.rasmussen@xxxxxxx
Cc: qais.yousef@xxxxxxx
Cc: rjw@xxxxxxxxxxxxx
Cc: tkjos@xxxxxxxxxx
Cc: valentin.schneider@xxxxxxx
Cc: vincent.guittot@xxxxxxxxxx
Fixes: eb92692b2544 ("sched/fair: Speed-up energy-aware wake-ups")
Link: https://lkml.kernel.org/r/20190920094115.GA11503@xxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index dfdac90..83ab35e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6389,7 +6389,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
}
/* Evaluate the energy impact of using this CPU. */
- if (max_spare_cap_cpu >= 0) {
+ if (max_spare_cap_cpu >= 0 && max_spare_cap_cpu != prev_cpu) {
cur_delta = compute_energy(p, max_spare_cap_cpu, pd);
cur_delta -= base_energy_pd;
if (cur_delta < best_delta) {
|