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 <[email protected]> AuthorDate: Fri, 20 Sep 2019 11:41:15 +02:00 Committer: Ingo Molnar <[email protected]> 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 <[email protected]> Signed-off-by: Quentin Perret <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Fixes: eb92692b2544 ("sched/fair: Speed-up energy-aware wake-ups") Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- 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) {
