Commit 4892f51a authored by Quentin Perret's avatar Quentin Perret Committed by Ingo Molnar

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: default avatarPavan Kondeti <pkondeti@codeaurora.org>
Signed-off-by: default avatarQuentin Perret <qperret@qperret.net>
Signed-off-by: default avatarPeter 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: dietmar.eggemann@arm.com
Cc: juri.lelli@redhat.com
Cc: morten.rasmussen@arm.com
Cc: qais.yousef@arm.com
Cc: rjw@rjwysocki.net
Cc: tkjos@google.com
Cc: valentin.schneider@arm.com
Cc: vincent.guittot@linaro.org
Fixes: eb92692b ("sched/fair: Speed-up energy-aware wake-ups")
Link: https://lkml.kernel.org/r/20190920094115.GA11503@qperret.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9fc41acc
...@@ -6389,7 +6389,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) ...@@ -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. */ /* 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 = compute_energy(p, max_spare_cap_cpu, pd);
cur_delta -= base_energy_pd; cur_delta -= base_energy_pd;
if (cur_delta < best_delta) { if (cur_delta < best_delta) {
......
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