Commit-ID: eaecf41f5abf80b63c8e025fcb9ee4aa203c3038
Gitweb: http://git.kernel.org/tip/eaecf41f5abf80b63c8e025fcb9ee4aa203c3038
Author: Morten Rasmussen <morten.rasmussen@xxxxxxx>
AuthorDate: Wed, 22 Jun 2016 18:03:14 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 10 Aug 2016 14:03:32 +0200
sched/fair: Optimize find_idlest_cpu() when there is no choice
In the current find_idlest_group()/find_idlest_cpu() search we end up
calling find_idlest_cpu() in a sched_group containing only one CPU in
the end. Checking idle-states becomes pointless when there is no
alternative, so bail out instead.
Signed-off-by: Morten Rasmussen <morten.rasmussen@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: dietmar.eggemann@xxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: mgalbraith@xxxxxxx
Cc: vincent.guittot@xxxxxxxxxx
Cc: yuyang.du@xxxxxxxxx
Link: http://lkml.kernel.org/r/1466615004-3503-4-git-send-email-morten.rasmussen@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d819da6..acdc351 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5239,6 +5239,10 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
int shallowest_idle_cpu = -1;
int i;
+ /* Check if we have any choice: */
+ if (group->group_weight == 1)
+ return cpumask_first(sched_group_cpus(group));
+
/* Traverse only the allowed CPUs */
for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
if (idle_cpu(i)) {
--
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