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sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target

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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 80e3d87b2c ("sched/rt: Reduce rq lock contention
by eliminating locking of non-feasible target") for rt class.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1431496867-4194-3-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Wanpeng Li 2015-05-13 14:01:03 +08:00 committed by Ingo Molnar
parent a6c0e746fb
commit 9d51426242
1 changed files with 14 additions and 1 deletions
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15
kernel/sched/deadline.c
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@ -1012,7 +1012,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
(p->nr_cpus_allowed > 1)) { (p->nr_cpus_allowed > 1)) {
int target = find_later_rq(p); 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; cpu = target;
} }
rcu_read_unlock(); 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); 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. */ /* Retry if something changed. */
if (double_lock_balance(rq, later_rq)) { if (double_lock_balance(rq, later_rq)) {
if (unlikely(task_rq(task) != rq || if (unlikely(task_rq(task) != rq ||