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Subject[PATCH v4 4/5] sched/deadline: Add support for SD_PREFER_SIBLING on find_later_rq()
Date
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.park@lge.com>
---
kernel/sched/deadline.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 0223694..ada264c 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1325,6 +1325,7 @@ static int find_later_rq(struct task_struct *task)
struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
int this_cpu = smp_processor_id();
int cpu = task_cpu(task);
+ int fallback_cpu = -1;

/* Make sure the mask is initialized first */
if (unlikely(!later_mask))
@@ -1385,6 +1386,15 @@ static int find_later_rq(struct task_struct *task)
* already under consideration through later_mask.
*/
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;
}
@@ -1393,6 +1403,13 @@ static int find_later_rq(struct task_struct *task)
rcu_read_unlock();

/*
+ * If fallback_cpu is valid, all our guesses failed *except* for
+ * SD_PREFER_SIBLING domain. Now, we can return the fallback cpu.
+ */
+ if (fallback_cpu != -1)
+ return fallback_cpu;
+
+ /*
* At this point, all our guesses failed, we just return
* 'something', and let the caller sort the things out.
*/
--
1.9.1
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