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

From: Wanpeng Li
Date: Mon Mar 23 2015 - 05:14:42 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>
---
kernel/sched/deadline.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 19d716e..9577db0 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -955,7 +955,8 @@ 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 &&
+ p->dl.deadline < cpu_rq(target)->dl.earliest_dl.curr)
cpu = target;
}
rcu_read_unlock();
--
1.9.1

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