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Date: Thu, 16 Feb 2017 11:05:53 +0900 From: Byungchul Park <byungchul.park@....com> To: <peterz@...radead.org>, <mingo@...nel.org> CC: <linux-kernel@...r.kernel.org>, <juri.lelli@...il.com>, <rostedt@...dmis.org>, <kernel-team@....com> Subject: [PATCH v2 1/2] sched/deadline: Remove unnecessary condition in push_dl_task() Once pick_next_pushable_dl_task(rq) returns a task, it guarantees that the task's cpu is rq->cpu, so task_cpu(next_task) is always rq->cpu if task == next_task. Remove the redundant condition and make code simpler. pick_next_pushable_dl_task(rq) has BUG_ON(rq->cpu != task_cpu(task)) when it returns a task other than NULL, which means that task_cpu(task) must be rq->cpu. So if task == next_task, then task_cpu(next_task) must be rq->cpu as well. By this patch, unnecessary one branch and two LOAD operations in 'if' statement can be avoided. Signed-off-by: Byungchul Park <byungchul.park@....com> --- kernel/sched/deadline.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 27737f3..ad8d577 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1483,7 +1483,7 @@ static int push_dl_task(struct rq *rq) * then possible that next_task has migrated. */ task = pick_next_pushable_dl_task(rq); - if (task_cpu(next_task) == rq->cpu && task == next_task) { + if (task == next_task) { /* * The task is still there. We don't try * again, some other cpu will pull it when ready. -- 1.9.1
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