Rework realtime priority support:

- Move the realtime priority range up above kernel sleep priorities and
  just below interrupt thread priorities.
- Contract the interrupt and kernel sleep priority ranges a bit so that
  the timesharing priority band can be increased.  The new timeshare range
  is now slightly larger than the old realtime + timeshare ranges.
- Change the ULE scheduler to no longer use realtime priorities for
  interactive threads.  Instead, the larger timeshare range is now split
  into separate subranges for interactive and non-interactive ("batch")
  threads.  The end result is that interactive threads and non-interactive
  threads still use the same priority ranges as before, but realtime
  threads now have a separate, dedicated priority range.
- Do not modify the priority of non-timeshare threads in sched_sleep()
  or via cv_broadcastpri().  Realtime and idle priority threads will
  no longer have their priorities affected by sleeping in the kernel.

Reviewed by:	jeff

1 files changed, 12 insertions, 4 deletions

diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c
index 8fa5f85..c1bb98f 100644
--- a/sys/kern/sched_ule.c
+++ b/sys/kern/sched_ule.c
@@ -118,11 +118,17 @@ static struct td_sched td_sched0;
 
 /*
  * Priority ranges used for interactive and non-interactive timeshare
- * threads.  Interactive threads use realtime priorities.
+ * threads.  The timeshare priorities are split up into four ranges.
+ * The first range handles interactive threads.  The last three ranges
+ * (NHALF, x, and NHALF) handle non-interactive threads with the outer
+ * ranges supporting nice values.
  */
-#define	PRI_MIN_INTERACT	PRI_MIN_REALTIME
-#define	PRI_MAX_INTERACT	PRI_MAX_REALTIME
-#define	PRI_MIN_BATCH		PRI_MIN_TIMESHARE
+#define	PRI_TIMESHARE_RANGE	(PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
+#define	PRI_INTERACT_RANGE	((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
+
+#define	PRI_MIN_INTERACT	PRI_MIN_TIMESHARE
+#define	PRI_MAX_INTERACT	(PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
+#define	PRI_MIN_BATCH		(PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
 #define	PRI_MAX_BATCH		PRI_MAX_TIMESHARE
 
 /*
@@ -1893,6 +1899,8 @@ sched_sleep(struct thread *td, int prio)
 	td->td_slptick = ticks;
 	if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
 		td->td_flags |= TDF_CANSWAP;
+	if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
+		return;
 	if (static_boost == 1 && prio)
 		sched_prio(td, prio);
 	else if (static_boost && td->td_priority > static_boost)