Commit-ID: eaecf41f5abf80b63c8e025fcb9ee4aa203c3038 Gitweb: http://git.kernel.org/tip/eaecf41f5abf80b63c8e025fcb9ee4aa203c3038 Author: Morten Rasmussen <morten.rasmus...@arm.com> AuthorDate: Wed, 22 Jun 2016 18:03:14 +0100 Committer: Ingo Molnar <mi...@kernel.org> 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.rasmus...@arm.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mike Galbraith <efa...@gmx.de> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: dietmar.eggem...@arm.com Cc: linux-kernel@vger.kernel.org Cc: mgalbra...@suse.de Cc: vincent.guit...@linaro.org Cc: yuyang...@intel.com Link: http://lkml.kernel.org/r/1466615004-3503-4-git-send-email-morten.rasmus...@arm.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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)) {
