- Make SCHED_STATS more generic by adding a wrapper to create the

   variables and sysctl nodes.
 - In reset walk the children of kern_sched_stats and reset the counters
   via the oid_arg1 pointer.  This allows us to add arbitrary counters to
   the tree and still reset them properly.
 - Define a set of switch types to be passed with flags to mi_switch().
   These types are named SWT_*.  These types correspond to SCHED_STATS
   counters and are automatically handled in this way.
 - Make the new SWT_ types more specific than the older switch stats.
   There are now stats for idle switches, remote idle wakeups, remote
   preemption ithreads idling, etc.
 - Add switch statistics for ULE's pickcpu algorithm.  These stats include
   how much migration there is, how often affinity was successful, how
   often threads were migrated to the local cpu on wakeup, etc.

Sponsored by:	Nokia

1 files changed, 30 insertions, 8 deletions

diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c
index 911b169..c03f7c8 100644
--- a/sys/kern/sched_ule.c
+++ b/sys/kern/sched_ule.c
@@ -909,7 +909,7 @@ tdq_idled(struct tdq *tdq)
 		}
 		spinlock_exit();
 		TDQ_UNLOCK(steal);
-		mi_switch(SW_VOL, NULL);
+		mi_switch(SW_VOL | SWT_IDLE, NULL);
 		thread_unlock(curthread);
 
 		return (0);
@@ -1073,6 +1073,13 @@ sched_setcpu(struct thread *td, int cpu, int flags)
 	return (tdq);
 }
 
+SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
+SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
+SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
+SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
+SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
+SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
+
 static int
 sched_pickcpu(struct thread *td, int flags)
 {
@@ -1098,8 +1105,10 @@ sched_pickcpu(struct thread *td, int flags)
 	 * the interrupt.
 	 */
 	if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
-	    curthread->td_intr_nesting_level)
+	    curthread->td_intr_nesting_level && ts->ts_cpu != self) {
+		SCHED_STAT_INC(pickcpu_intrbind);
 		ts->ts_cpu = self;
+	}
 	/*
 	 * If the thread can run on the last cpu and the affinity has not
 	 * expired or it is idle run it there.
@@ -1107,10 +1116,14 @@ sched_pickcpu(struct thread *td, int flags)
 	pri = td->td_priority;
 	tdq = TDQ_CPU(ts->ts_cpu);
 	if (THREAD_CAN_SCHED(td, ts->ts_cpu)) {
-		if (tdq->tdq_lowpri > PRI_MIN_IDLE)
+		if (tdq->tdq_lowpri > PRI_MIN_IDLE) {
+			SCHED_STAT_INC(pickcpu_idle_affinity);
 			return (ts->ts_cpu);
-		if (SCHED_AFFINITY(ts, CG_SHARE_L2) && tdq->tdq_lowpri > pri)
+		}
+		if (SCHED_AFFINITY(ts, CG_SHARE_L2) && tdq->tdq_lowpri > pri) {
+			SCHED_STAT_INC(pickcpu_affinity);
 			return (ts->ts_cpu);
+		}
 	}
 	/*
 	 * Search for the highest level in the tree that still has affinity.
@@ -1129,8 +1142,13 @@ sched_pickcpu(struct thread *td, int flags)
 	 * Compare the lowest loaded cpu to current cpu.
 	 */
 	if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
-	    TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
+	    TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE) {
+		SCHED_STAT_INC(pickcpu_local);
 		cpu = self;
+	} else
+		SCHED_STAT_INC(pickcpu_lowest);
+	if (cpu != ts->ts_cpu)
+		SCHED_STAT_INC(pickcpu_migration);
 	KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
 	return (cpu);
 }
@@ -1989,10 +2007,15 @@ sched_preempt(struct thread *td)
 	TDQ_LOCK_ASSERT(tdq, MA_OWNED);
 	tdq->tdq_ipipending = 0;
 	if (td->td_priority > tdq->tdq_lowpri) {
+		int flags;
+
+		flags = SW_INVOL | SW_PREEMPT;
 		if (td->td_critnest > 1)
 			td->td_owepreempt = 1;
+		else if (TD_IS_IDLETHREAD(td))
+			mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
 		else
-			mi_switch(SW_INVOL | SW_PREEMPT, NULL);
+			mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
 	}
 	thread_unlock(td);
 }
@@ -2378,8 +2401,7 @@ void
 sched_relinquish(struct thread *td)
 {
 	thread_lock(td);
-	SCHED_STAT_INC(switch_relinquish);
-	mi_switch(SW_VOL, NULL);
+	mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 	thread_unlock(td);
 }