From: Namhyung Kim <namhyung....@lge.com>
When sync wakeup happens and there's the waker task running alone,
select the target cpu as if it's already idle.
Cc: Mike Galbraith <efa...@gmx.de>
Cc: Suresh Siddha <suresh.b.sid...@intel.com>
Signed-off-by: Namhyung Kim <namhy...@kernel.org>
---
kernel/sched/fair.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d0cc03b3e70b..64b68bc82b52 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2632,7 +2632,7 @@ find_idlest_cpu(struct sched_group *group, struct
task_struct *p, int this_cpu)
/*
* Try and locate an idle CPU in the sched_domain.
*/
-static int select_idle_sibling(struct task_struct *p, int target)
+static int select_idle_sibling(struct task_struct *p, int target, int sync)
{
int cpu = smp_processor_id();
int prev_cpu = task_cpu(p);
@@ -2646,6 +2646,13 @@ static int select_idle_sibling(struct task_struct *p,
int target)
return cpu;
/*
+ * If the task is going to be woken-up on this cpu and there's only
+ * the sync-waker running, then it is the right target.
+ */
+ if (target == cpu && sync && this_rq()->nr_running == 1)
+ return cpu;
+
+ /*
* If the task is going to be woken-up on the cpu where it previously
* ran and if it is currently idle, then it the right target.
*/
@@ -2748,7 +2755,7 @@ select_task_rq_fair(struct task_struct *p, int sd_flag,
int wake_flags)
if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
prev_cpu = cpu;
- new_cpu = select_idle_sibling(p, prev_cpu);
+ new_cpu = select_idle_sibling(p, prev_cpu, sync);
goto unlock;
}
--
1.7.11.2
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