[RFC PATCH 7/7] sched/stats: Track the scan number of groups during load balance

[Chen Yu]

This metric could be used to evaluate the load balance cost and
effeciency.

Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
---
 include/linux/sched/topology.h | 1 +
 kernel/sched/fair.c            | 2 ++
 kernel/sched/stats.c           | 5 +++--
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index af2261308529..fa8fc6a497fd 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -124,6 +124,7 @@ struct sched_domain {
 	unsigned int lb_hot_gained[CPU_MAX_IDLE_TYPES];
 	unsigned int lb_nobusyg[CPU_MAX_IDLE_TYPES];
 	unsigned int lb_nobusyq[CPU_MAX_IDLE_TYPES];
+	unsigned int lb_sg_scan[CPU_MAX_IDLE_TYPES];
 
 	/* Active load balancing */
 	unsigned int alb_count;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9af57b5a24dc..96df7c5706d1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10253,6 +10253,8 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
 			goto next_group;
 
 
+		schedstat_inc(env->sd->lb_sg_scan[env->idle]);
+
 		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
 			sds->busiest = sg;
 			sds->busiest_stat = *sgs;
diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
index 857f837f52cb..38608f791363 100644
--- a/kernel/sched/stats.c
+++ b/kernel/sched/stats.c
@@ -152,7 +152,7 @@ static int show_schedstat(struct seq_file *seq, void *v)
 				   cpumask_pr_args(sched_domain_span(sd)));
 			for (itype = CPU_IDLE; itype < CPU_MAX_IDLE_TYPES;
 					itype++) {
-				seq_printf(seq, " %u %u %u %u %u %u %u %u",
+				seq_printf(seq, " %u %u %u %u %u %u %u %u %u",
 				    sd->lb_count[itype],
 				    sd->lb_balanced[itype],
 				    sd->lb_failed[itype],
@@ -160,7 +160,8 @@ static int show_schedstat(struct seq_file *seq, void *v)
 				    sd->lb_gained[itype],
 				    sd->lb_hot_gained[itype],
 				    sd->lb_nobusyq[itype],
-				    sd->lb_nobusyg[itype]);
+				    sd->lb_nobusyg[itype],
+				    sd->lb_sg_scan[itype]);
 			}
 			seq_printf(seq,
 				   " %u %u %u %u %u %u %u %u %u %u %u %u\n",
-- 
2.25.1