sched: schedule() speedup

speed up schedule(): share the 'now' parameter that deactivate_task()
was calculating internally.

( this also fixes the small accounting window between the deactivate
  call and the pick_next_task() call. )

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 0112f63..49f5b28 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -940,10 +940,9 @@ static inline void activate_idle_task(struct task_struct *p, struct rq *rq)
 /*
  * deactivate_task - remove a task from the runqueue.
  */
-static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep)
+static void
+deactivate_task(struct rq *rq, struct task_struct *p, int sleep, u64 now)
 {
-       u64 now = rq_clock(rq);
-
        if (p->state == TASK_UNINTERRUPTIBLE)
                rq->nr_uninterruptible++;
 
@@ -2122,7 +2121,7 @@ void sched_exec(void)
 static void pull_task(struct rq *src_rq, struct task_struct *p,
                      struct rq *this_rq, int this_cpu)
 {
-       deactivate_task(src_rq, p, 0);
+       deactivate_task(src_rq, p, 0, rq_clock(src_rq));
        set_task_cpu(p, this_cpu);
        activate_task(this_rq, p, 0);
        /*
@@ -3446,13 +3445,14 @@ need_resched_nonpreemptible:
 
        spin_lock_irq(&rq->lock);
        clear_tsk_need_resched(prev);
+       now = __rq_clock(rq);
 
        if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
                if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
                                unlikely(signal_pending(prev)))) {
                        prev->state = TASK_RUNNING;
                } else {
-                       deactivate_task(rq, prev, 1);
+                       deactivate_task(rq, prev, 1, now);
                }
                switch_count = &prev->nvcsw;
        }
@@ -3460,7 +3460,6 @@ need_resched_nonpreemptible:
        if (unlikely(!rq->nr_running))
                idle_balance(cpu, rq);
 
-       now = __rq_clock(rq);
        prev->sched_class->put_prev_task(rq, prev, now);
        next = pick_next_task(rq, prev, now);
 
@@ -4220,7 +4219,7 @@ recheck:
        }
        on_rq = p->se.on_rq;
        if (on_rq)
-               deactivate_task(rq, p, 0);
+               deactivate_task(rq, p, 0, rq_clock(rq));
        oldprio = p->prio;
        __setscheduler(rq, p, policy, param->sched_priority);
        if (on_rq) {
@@ -4973,7 +4972,7 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
 
        on_rq = p->se.on_rq;
        if (on_rq)
-               deactivate_task(rq_src, p, 0);
+               deactivate_task(rq_src, p, 0, rq_clock(rq_src));
        set_task_cpu(p, dest_cpu);
        if (on_rq) {
                activate_task(rq_dest, p, 0);
@@ -5387,7 +5386,7 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
                rq->migration_thread = NULL;
                /* Idle task back to normal (off runqueue, low prio) */
                rq = task_rq_lock(rq->idle, &flags);
-               deactivate_task(rq, rq->idle, 0);
+               deactivate_task(rq, rq->idle, 0, rq_clock(rq));
                rq->idle->static_prio = MAX_PRIO;
                __setscheduler(rq, rq->idle, SCHED_NORMAL, 0);
                rq->idle->sched_class = &idle_sched_class;
@@ -6626,7 +6625,7 @@ void normalize_rt_tasks(void)
 
                on_rq = p->se.on_rq;
                if (on_rq)
-                       deactivate_task(task_rq(p), p, 0);
+                       deactivate_task(task_rq(p), p, 0, rq_clock(task_rq(p)));
                __setscheduler(rq, p, SCHED_NORMAL, 0);
                if (on_rq) {
                        activate_task(task_rq(p), p, 0);