From a65ac745e47e91f9d98dbf07f22ed0492e34d998 Mon Sep 17 00:00:00 2001 From: Jupyung Lee Date: Tue, 17 Nov 2009 18:51:40 +0900 Subject: [PATCH] sched: Move update_curr() in check_preempt_wakeup() to avoid redundant call If a RT task is woken up while a non-RT task is running, check_preempt_wakeup() is called to check whether the new task can preempt the old task. The function returns quickly without going deeper because it is apparent that a RT task can always preempt a non-RT task. In this situation, check_preempt_wakeup() always calls update_curr() to update vruntime value of the currently running task. However, the function call is unnecessary and redundant at that moment because (1) a non-RT task can always be preempted by a RT task regardless of its vruntime value, and (2) update_curr() will be called shortly when the context switch between two occurs. By moving update_curr() in check_preempt_wakeup(), we can avoid redundant call to update_curr(), slightly reducing the time taken to wake up RT tasks. Signed-off-by: Jupyung Lee [ Place update_curr() right before the wake_preempt_entity() call, which is the only thing that relies on the updated vruntime ] Signed-off-by: Peter Zijlstra LKML-Reference: <1258451500-6714-1-git-send-email-jupyung@gmail.com> Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 44ec80ccfa85..4dec18579c9a 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1651,8 +1651,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ int sync = wake_flags & WF_SYNC; int scale = cfs_rq->nr_running >= sched_nr_latency; - update_curr(cfs_rq); - if (unlikely(rt_prio(p->prio))) { resched_task(curr); return; @@ -1710,6 +1708,8 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ BUG_ON(!pse); + update_curr(cfs_rq); + if (wakeup_preempt_entity(se, pse) == 1) { resched_task(curr); /*