Commit-ID: 9d514262425691dddf942edea8bc9919e66fe140
Gitweb: http://git.kernel.org/tip/9d514262425691dddf942edea8bc9919e66fe140
Author: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
AuthorDate: Wed, 13 May 2015 14:01:03 +0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 19 Jun 2015 10:06:46 +0200
sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target
This patch adds a check 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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1431496867-4194-3-git-send-email-wanpeng.li@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/deadline.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1c4bc31..98f7871 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1012,7 +1012,9 @@ 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();
@@ -1359,6 +1361,17 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
later_rq = cpu_rq(cpu);
+ if (!dl_time_before(task->dl.deadline,
+ later_rq->dl.earliest_dl.curr)) {
+ /*
+ * Target rq has tasks of equal or earlier deadline,
+ * retrying does not release any lock and is unlikely
+ * to yield a different result.
+ */
+ later_rq = NULL;
+ break;
+ }
+
/* Retry if something changed. */
if (double_lock_balance(rq, later_rq)) {
if (unlikely(task_rq(task) != rq ||
--
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