sched: de-SCHED_OTHER-ize the RT path

The current wake-up code path tries to determine if it can optimize the
wake-up to "this_cpu" by computing load calculations.  The problem is that
these calculations are only relevant to SCHED_OTHER tasks where load is king.
For RT tasks, priority is king.  So the load calculation is completely wasted
bandwidth.

Therefore, we create a new sched_class interface to help with
pre-wakeup routing decisions and move the load calculation as a function
of CFS task's class.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 0 deletions

diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index bf9c25c15b8b..ca5374860aef 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -5,6 +5,12 @@
  *  handled in sched_fair.c)
  */
 
+#ifdef CONFIG_SMP
+static int select_task_rq_idle(struct task_struct *p, int sync)
+{
+        return task_cpu(p); /* IDLE tasks as never migrated */
+}
+#endif /* CONFIG_SMP */
 /*
  * Idle tasks are unconditionally rescheduled:
  */
@@ -72,6 +78,9 @@ const struct sched_class idle_sched_class = {
 
         /* dequeue is not valid, we print a debug message there: */
         .dequeue_task           = dequeue_task_idle,
+#ifdef CONFIG_SMP
+        .select_task_rq         = select_task_rq_idle,
+#endif /* CONFIG_SMP */
 
         .check_preempt_curr     = check_preempt_curr_idle,