[RFC][PATCH 1/2] sched: Start tracking SCHED_IDLE tasks count in cfs_rq

[Viresh Kumar]

Start tracking how many tasks with SCHED_IDLE policy are present in each
cfs_rq. This will be used by later commits.

Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
 kernel/sched/fair.c  | 14 ++++++++++++--
 kernel/sched/sched.h |  2 ++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e30dea59d215..ad0b09ddddc0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4453,7 +4453,7 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
 	struct rq *rq = rq_of(cfs_rq);
 	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
 	struct sched_entity *se;
-	long task_delta, dequeue = 1;
+	long task_delta, idle_task_delta, dequeue = 1;
 	bool empty;
 
 	se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
@@ -4464,6 +4464,7 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
 	rcu_read_unlock();
 
 	task_delta = cfs_rq->h_nr_running;
+	idle_task_delta = cfs_rq->idle_h_nr_running;
 	for_each_sched_entity(se) {
 		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
 		/* throttled entity or throttle-on-deactivate */
@@ -4473,6 +4474,7 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
 		if (dequeue)
 			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
 		qcfs_rq->h_nr_running -= task_delta;
+		qcfs_rq->idle_h_nr_running -= idle_task_delta;
 
 		if (qcfs_rq->load.weight)
 			dequeue = 0;
@@ -4512,7 +4514,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
 	struct sched_entity *se;
 	int enqueue = 1;
-	long task_delta;
+	long task_delta, idle_task_delta;
 
 	se = cfs_rq->tg->se[cpu_of(rq)];
 
@@ -4532,6 +4534,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 		return;
 
 	task_delta = cfs_rq->h_nr_running;
+	idle_task_delta = cfs_rq->idle_h_nr_running;
 	for_each_sched_entity(se) {
 		if (se->on_rq)
 			enqueue = 0;
@@ -4540,6 +4543,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 		if (enqueue)
 			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
 		cfs_rq->h_nr_running += task_delta;
+		cfs_rq->idle_h_nr_running += idle_task_delta;
 
 		if (cfs_rq_throttled(cfs_rq))
 			break;
@@ -5092,6 +5096,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 {
 	struct cfs_rq *cfs_rq;
 	struct sched_entity *se = &p->se;
+	int idle_h_nr_running = unlikely(task_has_idle_policy(p)) ? 1 : 0;
 
 	/*
 	 * The code below (indirectly) updates schedutil which looks at
@@ -5124,6 +5129,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		if (cfs_rq_throttled(cfs_rq))
 			break;
 		cfs_rq->h_nr_running++;
+		cfs_rq->idle_h_nr_running += idle_h_nr_running;
 
 		flags = ENQUEUE_WAKEUP;
 	}
@@ -5131,6 +5137,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 	for_each_sched_entity(se) {
 		cfs_rq = cfs_rq_of(se);
 		cfs_rq->h_nr_running++;
+		cfs_rq->idle_h_nr_running += idle_h_nr_running;
 
 		if (cfs_rq_throttled(cfs_rq))
 			break;
@@ -5157,6 +5164,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 	struct cfs_rq *cfs_rq;
 	struct sched_entity *se = &p->se;
 	int task_sleep = flags & DEQUEUE_SLEEP;
+	int idle_h_nr_running = unlikely(task_has_idle_policy(p)) ? 1 : 0;
 
 	for_each_sched_entity(se) {
 		cfs_rq = cfs_rq_of(se);
@@ -5171,6 +5179,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		if (cfs_rq_throttled(cfs_rq))
 			break;
 		cfs_rq->h_nr_running--;
+		cfs_rq->idle_h_nr_running -= idle_h_nr_running;
 
 		/* Don't dequeue parent if it has other entities besides us */
 		if (cfs_rq->load.weight) {
@@ -5190,6 +5199,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 	for_each_sched_entity(se) {
 		cfs_rq = cfs_rq_of(se);
 		cfs_rq->h_nr_running--;
+		cfs_rq->idle_h_nr_running -= idle_h_nr_running;
 
 		if (cfs_rq_throttled(cfs_rq))
 			break;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e0e052a50fcd..86a388c506ac 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -488,6 +488,8 @@ struct cfs_rq {
 	unsigned long		runnable_weight;
 	unsigned int		nr_running;
 	unsigned int		h_nr_running;
+	/* h_nr_running for SCHED_IDLE tasks */
+	unsigned int		idle_h_nr_running;
 
 	u64			exec_clock;
 	u64			min_vruntime;
-- 
2.19.1.568.g152ad8e3369a