sched: optimize task_tick_rt() a bit
Mitchell Erblich suggested a quality-of-implementation change to
not requeue SCHED_RR tasks if there's only a single task on the
runqueue, by checking for rq->nr_running == 1.
provide a more efficient implementation of that, to check that
particular RT priority-queue only.
[ From: mingo@elte.hu ]
Also first requeue the task then set need_resched - results in slightly
better machine-instruction ordering. Also clean up the code a bit.
Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index dcdcad6..4b87476 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -207,10 +207,15 @@
return;
p->time_slice = static_prio_timeslice(p->static_prio);
- set_tsk_need_resched(p);
- /* put it at the end of the queue: */
- requeue_task_rt(rq, p);
+ /*
+ * Requeue to the end of queue if we are not the only element
+ * on the queue:
+ */
+ if (p->run_list.prev != p->run_list.next) {
+ requeue_task_rt(rq, p);
+ set_tsk_need_resched(p);
+ }
}
static struct sched_class rt_sched_class __read_mostly = {