Index: kern/sched_ule.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/sched_ule.c,v
retrieving revision 1.243
diff -u -r1.243 sched_ule.c
--- kern/sched_ule.c	17 Apr 2008 09:56:01 -0000	1.243
+++ kern/sched_ule.c	22 Apr 2008 12:21:17 -0000
@@ -2201,29 +2201,58 @@
 	return (PCPU_GET(idlethread));
 }
 
+int oldresched = 0;
+
 /*
  * Set owepreempt if necessary.  Preemption never happens directly in ULE,
- * we always request it once we exit a critical section.
+ * we always request it once we exit a critical section.  If preemption is
+ * not set we may conditionally set NEEDRESCHED if the woken thread should
+ * be running.
  */
 static inline void
 sched_setpreempt(struct thread *td)
 {
 	struct thread *ctd;
+	struct tdq *tdq;
 	int cpri;
 	int pri;
+	u_char cdelta;
+	u_char delta;
 
 	THREAD_LOCK_ASSERT(curthread, MA_OWNED);
 
 	ctd = curthread;
 	pri = td->td_priority;
 	cpri = ctd->td_priority;
-	if (pri < cpri)
+	if (oldresched && pri < cpri)
 		ctd->td_flags |= TDF_NEEDRESCHED;
 	if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
 		return;
-	if (!sched_shouldpreempt(pri, cpri, 0))
+	if (sched_shouldpreempt(pri, cpri, 0)) {
+		ctd->td_owepreempt = 1;
+		return;
+	}
+	if (oldresched)
+		return;
+	/*
+	 * Timeshare threads require special checks to see if the newly
+	 * woken thread should be run straight away or if the existing
+	 * thread may continue.
+	 */
+	tdq = TDQ_SELF();
+	if (ctd->td_sched->ts_runq != &tdq->tdq_timeshare ||
+	    td->td_sched->ts_runq != &tdq->tdq_timeshare) {
+		ctd->td_flags |= TDF_NEEDRESCHED;
 		return;
-	ctd->td_owepreempt = 1;
+	}
+	/*
+	 * Compute the distance from the head of the queue.  If the new
+	 * thread is closer than curthread force a reschedule.
+	 */
+	cdelta = (ctd->td_rqindex - tdq->tdq_ridx) % RQ_NQS;
+	delta = (td->td_rqindex - tdq->tdq_ridx) % RQ_NQS;
+	if (delta < cdelta)
+		ctd->td_flags |= TDF_NEEDRESCHED;
 }
 
 /*
@@ -2588,6 +2617,8 @@
      0,"Number of times idle will spin waiting for new work.");
 SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW, &sched_idlespinthresh,
      0,"Threshold before we will permit idle spinning.");
+SYSCTL_INT(_kern_sched, OID_AUTO, oldresched, CTLFLAG_RW, &oldresched,
+     0,"Threshold before we will permit idle spinning.");
 #ifdef SMP
 SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
     "Number of hz ticks to keep thread affinity for");