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 <qper...@qperret.net>
AuthorDate: Fri, 20 Sep 2019 11:41:15 +02:00
Committer: Ingo Molnar <mi...@kernel.org>
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 <pkond...@codeaurora.org>
Signed-off-by: Quentin Perret <qper...@qperret.net>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: dietmar.eggem...@arm.com
Cc: juri.le...@redhat.com
Cc: morten.rasmus...@arm.com
Cc: qais.you...@arm.com
Cc: r...@rjwysocki.net
Cc: tk...@google.com
Cc: valentin.schnei...@arm.com
Cc: vincent.guit...@linaro.org
Fixes: eb92692b2544 ("sched/fair: Speed-up energy-aware wake-ups")
Link: https://lkml.kernel.org/r/20190920094115.ga11...@qperret.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
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) {
