sched: Add statistic for newidle load balance cost

Tracking rq->max_idle_balance_cost and sd->max_newidle_lb_cost.
It's useful to know these values in debug mode.

Signed-off-by: Alex Shi <alex.shi@linaro.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/52E0F3BF.5020904@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

@@ -4811,7 +4811,7 @@ set_table_entry(struct ctl_table *entry,
 static struct ctl_table *
 sd_alloc_ctl_domain_table(struct sched_domain *sd)
 {
-	struct ctl_table *table = sd_alloc_ctl_entry(13);
+	struct ctl_table *table = sd_alloc_ctl_entry(14);
 
 	if (table == NULL)
 		return NULL;
@@ -4839,9 +4839,12 @@ sd_alloc_ctl_domain_table(struct sched_domain *sd)
 		sizeof(int), 0644, proc_dointvec_minmax, false);
 	set_table_entry(&table[10], "flags", &sd->flags,
 		sizeof(int), 0644, proc_dointvec_minmax, false);
-	set_table_entry(&table[11], "name", sd->name,
+	set_table_entry(&table[11], "max_newidle_lb_cost",
+		&sd->max_newidle_lb_cost,
+		sizeof(long), 0644, proc_doulongvec_minmax, false);
+	set_table_entry(&table[12], "name", sd->name,
 		CORENAME_MAX_SIZE, 0444, proc_dostring, false);
-	/* &table[12] is terminator */
+	/* &table[13] is terminator */
 
 	return table;
 }

kernel/sched/debug.c

@@ -321,6 +321,7 @@ do {									\
 	P(sched_goidle);
 #ifdef CONFIG_SMP
 	P64(avg_idle);
+	P64(max_idle_balance_cost);
 #endif
 
 	P(ttwu_count);