On Mon, 2016-05-23 at 11:58 +0100, Morten Rasmussen wrote:
> 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.
>
> cc: Ingo Molnar <mi...@redhat.com>
> cc: Peter Zijlstra <pet...@infradead.org>
>
> Signed-off-by: Morten Rasmussen <morten.rasmus...@arm.com>
> ---
> kernel/sched/fair.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 0fe3020..564215d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5155,6 +5155,11 @@ 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));
> +> > }
> +
Hm, if task isn't allowed there, too bad?
> /* Traverse only the allowed CPUs */
> > > for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
> > > > if (idle_cpu(i)) {
