- Add a sched API entry point that returns the system load. This load should

not include any ithreads.
 - Document the difference between sched_load() and sched_runnable() as they
   are very similar.

sys/sys/sched.h

@@ -31,7 +31,14 @@
 
 /*
  * General scheduling info.
+ *
+ * sched_load:
+ *	Total runnable non-ithread threads in the system.
+ *
+ * sched_runnable:
+ *	Runnable threads for this processor.
  */
+int	sched_load(void);
 int	sched_rr_interval(void);
 int	sched_runnable(void);