Messages in this thread Patch in this message | | | From | Wanpeng Li <> | Subject | [PATCH v2 3/7] sched/deadline: reduce rq lock contention by eliminating locking of non-feasible target | Date | Wed, 13 May 2015 14:01:03 +0800 |
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This patch adds 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@linux.intel.com> --- v1 -> v2: * add check in find_lock_later_rq()
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 4303af2..e49b1e6 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(); @@ -1360,6 +1362,17 @@ 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 || -- 1.9.1
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