Likelihood of rt_tasks

[Con Kolivas]

A quick question about the usefulness of making rt_task() checks 
unlikely in sched-unlikely-rt_task.patch which is in -mm

quote:

diff -puN include/linux/sched.h~sched-unlikely-rt_task include/linux/sched.h
--- 25/include/linux/sched.h~sched-unlikely-rt_task	Fri Jul  2 16:33:01 2004
+++ 25-akpm/include/linux/sched.h	Fri Jul  2 16:33:01 2004
@@ -300,7 +300,7 @@ struct signal_struct {

 #define MAX_PRIO		(MAX_RT_PRIO + 40)

-#define rt_task(p)		((p)->prio < MAX_RT_PRIO)
+#define rt_task(p)		(unlikely((p)->prio < MAX_RT_PRIO))

 /*
  * Some day this will be a full-fledged user tracking system..

---
While rt tasks are normally unlikely, what happens in the case when you 
are scheduling one or many running rt_tasks and the majority of your 
scheduling is rt? Would it be such a good idea in this setting that it 
is always hitting the slow path of branching all the time?

Con

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