[PATCH 1/6] sched/rt: check if curr can be pushed/pulled somewhere else in advance

Wanpeng Li
2014-10-27T01:41:36Z

This patch checks if current can be pushed/pulled somewhere else
in advance to make logic clear.

- If current can't be migrated, useless to reschedule, let's hope
task can move out.
- If task is migratable, so let's not schedule it and see if it
can be pushed or pulled somewhere else.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
kernel/sched/rt.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 87ea5bf..ca1b7c7 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1351,16 +1351,22 @@ out:

static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
{
- if (rq->curr->nr_cpus_allowed == 1)
+ /*
+ * Current can't be migrated, useless to reschedule,
+ * let's hope p can move out.
+ */
+ if (rq->curr->nr_cpus_allowed == 1 ||
+ !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
return;

+ /*
+ * p is migratable, so let's not schedule it and
+ * see if it is pushed or pulled somewhere else.
+ */
if (p->nr_cpus_allowed != 1
&& cpupri_find(&rq->rd->cpupri, p, NULL))
return;

- if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
- return;
-
/*
* There appears to be other cpus that can accept
* current and none to run 'p', so lets reschedule
--
1.9.1