[PATCH v2] sched/deadline: reduce rq lock contention by eliminating locking of non-feasible target

From: Wanpeng Li
Date: Mon Mar 23 2015 - 05:20:29 EST


This patch adds checks that prevents futile attempts to move dl tasks to
a CPU with active tasks of equal or earlier deadline. The same behavior as
commit 80e3d87b2c55 ("sched/rt: Reduce rq lock contention by eliminating
locking of non-feasible target") for rt class.

Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
---
v1 -> v2:
* use dl_time_before macro

kernel/sched/deadline.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 19d716e..f48d319 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -955,7 +955,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
(p->nr_cpus_allowed > 1)) {
int target = find_later_rq(p);

- if (target != -1)
+ if (target != -1 &&
+ dl_time_before(p->dl.deadline,
+ cpu_rq(target)->dl.earliest_dl.curr))
cpu = target;
}
rcu_read_unlock();
--
1.9.1

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