sched/fair: Add new cfs_rq.h_nr_runnable

With delayed dequeued feature, a sleeping sched_entity remains queued in
the rq until its lag has elapsed. As a result, it stays also visible
in the statistics that are used to balance the system and in particular
the field cfs.h_nr_queued when the sched_entity is associated to a task.

Create a new h_nr_runnable that tracks only queued and runnable tasks.

Signed-off-by: Vincent Guittot <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Dietmar Eggemann <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: vingu-linaro

kernel/sched/debug.c

@@ -844,6 +844,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
 	spread = right_vruntime - left_vruntime;
 	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", "spread", SPLIT_NS(spread));
 	SEQ_printf(m, "  .%-30s: %d\n", "nr_running", cfs_rq->nr_running);
+	SEQ_printf(m, "  .%-30s: %d\n", "h_nr_runnable", cfs_rq->h_nr_runnable);
 	SEQ_printf(m, "  .%-30s: %d\n", "h_nr_queued", cfs_rq->h_nr_queued);
 	SEQ_printf(m, "  .%-30s: %d\n", "h_nr_delayed", cfs_rq->h_nr_delayed);
 	SEQ_printf(m, "  .%-30s: %d\n", "idle_nr_running",

kernel/sched/fair.c

@@ -5469,6 +5469,7 @@ static void set_delayed(struct sched_entity *se)
 	for_each_sched_entity(se) {
 		struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
+		cfs_rq->h_nr_runnable--;
 		cfs_rq->h_nr_delayed++;
 		if (cfs_rq_throttled(cfs_rq))
 			break;
@@ -5481,6 +5482,7 @@ static void clear_delayed(struct sched_entity *se)
 	for_each_sched_entity(se) {
 		struct cfs_rq *cfs_rq = cfs_rq_of(se);
 
+		cfs_rq->h_nr_runnable++;
 		cfs_rq->h_nr_delayed--;
 		if (cfs_rq_throttled(cfs_rq))
 			break;
@@ -5930,7 +5932,7 @@ static bool 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 queued_delta, idle_task_delta, delayed_delta, dequeue = 1;
+	long queued_delta, runnable_delta, idle_task_delta, delayed_delta, dequeue = 1;
 	long rq_h_nr_queued = rq->cfs.h_nr_queued;
 
 	raw_spin_lock(&cfs_b->lock);
@@ -5962,6 +5964,7 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
 	rcu_read_unlock();
 
 	queued_delta = cfs_rq->h_nr_queued;
+	runnable_delta = cfs_rq->h_nr_runnable;
 	idle_task_delta = cfs_rq->idle_h_nr_running;
 	delayed_delta = cfs_rq->h_nr_delayed;
 	for_each_sched_entity(se) {
@@ -5986,6 +5989,7 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
 			idle_task_delta = cfs_rq->h_nr_queued;
 
 		qcfs_rq->h_nr_queued -= queued_delta;
+		qcfs_rq->h_nr_runnable -= runnable_delta;
 		qcfs_rq->idle_h_nr_running -= idle_task_delta;
 		qcfs_rq->h_nr_delayed -= delayed_delta;
 
@@ -6009,6 +6013,7 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
 			idle_task_delta = cfs_rq->h_nr_queued;
 
 		qcfs_rq->h_nr_queued -= queued_delta;
+		qcfs_rq->h_nr_runnable -= runnable_delta;
 		qcfs_rq->idle_h_nr_running -= idle_task_delta;
 		qcfs_rq->h_nr_delayed -= delayed_delta;
 	}
@@ -6036,7 +6041,7 @@ void unthrottle_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 queued_delta, idle_task_delta, delayed_delta;
+	long queued_delta, runnable_delta, idle_task_delta, delayed_delta;
 	long rq_h_nr_queued = rq->cfs.h_nr_queued;
 
 	se = cfs_rq->tg->se[cpu_of(rq)];
@@ -6071,6 +6076,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	}
 
 	queued_delta = cfs_rq->h_nr_queued;
+	runnable_delta = cfs_rq->h_nr_runnable;
 	idle_task_delta = cfs_rq->idle_h_nr_running;
 	delayed_delta = cfs_rq->h_nr_delayed;
 	for_each_sched_entity(se) {
@@ -6089,6 +6095,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 			idle_task_delta = cfs_rq->h_nr_queued;
 
 		qcfs_rq->h_nr_queued += queued_delta;
+		qcfs_rq->h_nr_runnable += runnable_delta;
 		qcfs_rq->idle_h_nr_running += idle_task_delta;
 		qcfs_rq->h_nr_delayed += delayed_delta;
 
@@ -6107,6 +6114,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 			idle_task_delta = cfs_rq->h_nr_queued;
 
 		qcfs_rq->h_nr_queued += queued_delta;
+		qcfs_rq->h_nr_runnable += runnable_delta;
 		qcfs_rq->idle_h_nr_running += idle_task_delta;
 		qcfs_rq->h_nr_delayed += delayed_delta;
 
@@ -7021,6 +7029,8 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		enqueue_entity(cfs_rq, se, flags);
 		slice = cfs_rq_min_slice(cfs_rq);
 
+		if (!h_nr_delayed)
+			cfs_rq->h_nr_runnable++;
 		cfs_rq->h_nr_queued++;
 		cfs_rq->idle_h_nr_running += idle_h_nr_running;
 		cfs_rq->h_nr_delayed += h_nr_delayed;
@@ -7045,6 +7055,8 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		se->slice = slice;
 		slice = cfs_rq_min_slice(cfs_rq);
 
+		if (!h_nr_delayed)
+			cfs_rq->h_nr_runnable++;
 		cfs_rq->h_nr_queued++;
 		cfs_rq->idle_h_nr_running += idle_h_nr_running;
 		cfs_rq->h_nr_delayed += h_nr_delayed;
@@ -7135,6 +7147,8 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
 			break;
 		}
 
+		if (!h_nr_delayed)
+			cfs_rq->h_nr_runnable -= h_nr_queued;
 		cfs_rq->h_nr_queued -= h_nr_queued;
 		cfs_rq->idle_h_nr_running -= idle_h_nr_running;
 		cfs_rq->h_nr_delayed -= h_nr_delayed;
@@ -7174,6 +7188,8 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
 		se->slice = slice;
 		slice = cfs_rq_min_slice(cfs_rq);
 
+		if (!h_nr_delayed)
+			cfs_rq->h_nr_runnable -= h_nr_queued;
 		cfs_rq->h_nr_queued -= h_nr_queued;
 		cfs_rq->idle_h_nr_running -= idle_h_nr_running;
 		cfs_rq->h_nr_delayed -= h_nr_delayed;

kernel/sched/sched.h

@@ -647,6 +647,7 @@ struct cfs_rq {
 	struct load_weight	load;
 	unsigned int		nr_running;
 	unsigned int		h_nr_queued;       /* SCHED_{NORMAL,BATCH,IDLE} */
+	unsigned int		h_nr_runnable;     /* SCHED_{NORMAL,BATCH,IDLE} */
 	unsigned int		idle_nr_running;   /* SCHED_IDLE */
 	unsigned int		idle_h_nr_running; /* SCHED_IDLE */
 	unsigned int		h_nr_delayed;