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.
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
