On Thu, Mar 23, 2017 at 11:12:49AM +0900, Byungchul Park wrote:
> It would be better to avoid pushing tasks to other cpu within
> a SD_PREFER_SIBLING domain, instead, get more chances to check other
> siblings.
+cc ghask...@novell.com
+cc srost...@redhat.com
>
> Signed-off-by: Byungchul Park <byungchul.p...@lge.com>
> ---
> kernel/sched/rt.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 979b734..6332b2ad 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -1624,6 +1624,7 @@ static int find_lowest_rq(struct task_struct *task)
> struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask);
> int this_cpu = smp_processor_id();
> int cpu = task_cpu(task);
> + int fallback_cpu = -1;
>
> /* Make sure the mask is initialized first */
> if (unlikely(!lowest_mask))
> @@ -1671,6 +1672,15 @@ static int find_lowest_rq(struct task_struct *task)
> best_cpu = cpumask_first_and(lowest_mask,
> sched_domain_span(sd));
> if (best_cpu < nr_cpu_ids) {
> + /*
> + * If current domain is SD_PREFER_SIBLING
> + * flaged, we have to get more chances to
> + * check other siblings.
> + */
> + if (sd->flags & SD_PREFER_SIBLING) {
> + fallback_cpu = best_cpu;
> + continue;
> + }
> rcu_read_unlock();
> return best_cpu;
> }
> @@ -1679,6 +1689,13 @@ static int find_lowest_rq(struct task_struct *task)
> rcu_read_unlock();
>
> /*
> + * If fallback_cpu is valid, all our quesses failed *except* for
> + * SD_PREFER_SIBLING domain. Now, we can return the fallback cpu.
> + */
> + if (fallback_cpu != -1)
> + return fallback_cpu;
> +
> + /*
> * And finally, if there were no matches within the domains
> * just give the caller *something* to work with from the compatible
> * locations.
> --
> 1.9.1
