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

sys/kern/sched_4bsd.c

@@ -908,7 +908,7 @@ sched_sleep(struct thread *td, int pri)
 	THREAD_LOCK_ASSERT(td, MA_OWNED);
 	td->td_slptick = ticks;
 	td->td_sched->ts_slptime = 0;
-	if (pri)
+	if (pri != 0 && PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 		sched_prio(td, pri);
 	if (TD_IS_SUSPENDED(td) || pri >= PSOCK)
 		td->td_flags |= TDF_CANSWAP;

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)

sys/kern/subr_sleepqueue.c

@@ -745,7 +745,8 @@ sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
 
 	/* Adjust priority if requested. */
 	MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
-	if (pri != 0 && td->td_priority > pri)
+	if (pri != 0 && td->td_priority > pri &&
+	    PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
 		sched_prio(td, pri);
 
 	/*

sys/sys/priority.h

@@ -67,10 +67,10 @@
  * Priorities range from 0 to 255, but differences of less then 4 (RQ_PPQ)
  * are insignificant.  Ranges are as follows:
  *
- * Interrupt threads:		0 - 63
- * Top half kernel threads:	64 - 127
- * Realtime user threads:	128 - 159
- * Time sharing user threads:	160 - 223
+ * Interrupt threads:		0 - 47
+ * Realtime user threads:	48 - 79
+ * Top half kernel threads:	80 - 119
+ * Time sharing user threads:	120 - 223
  * Idle user threads:		224 - 255
  *
  * XXX If/When the specific interrupt thread and top half thread ranges
@@ -81,7 +81,7 @@
 #define	PRI_MAX			(255)		/* Lowest priority. */
 
 #define	PRI_MIN_ITHD		(PRI_MIN)
-#define	PRI_MAX_ITHD		(PRI_MIN_KERN - 1)
+#define	PRI_MAX_ITHD		(PRI_MIN_REALTIME - 1)
 
 #define	PI_REALTIME		(PRI_MIN_ITHD + 0)
 #define	PI_AV			(PRI_MIN_ITHD + 4)
@@ -92,8 +92,11 @@
 #define	PI_SOFT			(PRI_MIN_ITHD + 24)
 #define	PI_SWI(x)		(PI_SOFT + (x) * RQ_PPQ)
 
-#define	PRI_MIN_KERN		(64)
-#define	PRI_MAX_KERN		(PRI_MIN_REALTIME - 1)
+#define	PRI_MIN_REALTIME	(48)
+#define	PRI_MAX_REALTIME	(PRI_MIN_KERN - 1)
+
+#define	PRI_MIN_KERN		(80)
+#define	PRI_MAX_KERN		(PRI_MIN_TIMESHARE - 1)
 
 #define	PSWP			(PRI_MIN_KERN + 0)
 #define	PVM			(PRI_MIN_KERN + 4)
@@ -106,10 +109,7 @@
 #define	PLOCK			(PRI_MIN_KERN + 32)
 #define	PPAUSE			(PRI_MIN_KERN + 36)
 
-#define	PRI_MIN_REALTIME	(128)
-#define	PRI_MAX_REALTIME	(PRI_MIN_TIMESHARE - 1)
-
-#define	PRI_MIN_TIMESHARE	(160)
+#define	PRI_MIN_TIMESHARE	(120)
 #define	PRI_MAX_TIMESHARE	(PRI_MIN_IDLE - 1)
 
 #define	PUSER			(PRI_MIN_TIMESHARE)