[RFC 19/60] sched: Add entity variants of enqueue_task_fair() and dequeue_task_fair()

["Jan H. Schönherr" <jschoenh@amazon.de>]

There is fair amount of overlap between enqueue_task_fair() and
unthrottle_cfs_rq(), as well as between dequeue_task_fair() and
throttle_cfs_rq(). This is the first step toward having both of
them use the same basic function.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
---
 kernel/sched/fair.c  | 82 ++++++++++++++++++++++++++++++----------------------
 kernel/sched/sched.h |  3 ++
 2 files changed, 51 insertions(+), 34 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9f63ac37f5ef..a96328c5a864 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4979,32 +4979,9 @@ static inline void hrtick_update(struct rq *rq)
 }
 #endif
 
-/*
- * The enqueue_task method is called before nr_running is
- * increased. Here we update the fair scheduling stats and
- * then put the task into the rbtree:
- */
-static void
-enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
+bool enqueue_entity_fair(struct rq *rq, struct sched_entity *se, int flags)
 {
 	struct cfs_rq *cfs_rq;
-	struct sched_entity *se = &p->se;
-
-	/*
-	 * The code below (indirectly) updates schedutil which looks at
-	 * the cfs_rq utilization to select a frequency.
-	 * Let's add the task's estimated utilization to the cfs_rq's
-	 * estimated utilization, before we update schedutil.
-	 */
-	util_est_enqueue(&rq->cfs, p);
-
-	/*
-	 * If in_iowait is set, the code below may not trigger any cpufreq
-	 * utilization updates, so do it here explicitly with the IOWAIT flag
-	 * passed.
-	 */
-	if (p->in_iowait)
-		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
 
 	for_each_sched_entity(se) {
 		if (se->on_rq)
@@ -5036,7 +5013,38 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		update_cfs_group(se);
 	}
 
-	if (!se)
+	return se != NULL;
+}
+
+/*
+ * The enqueue_task method is called before nr_running is
+ * increased. Here we update the fair scheduling stats and
+ * then put the task into the rbtree:
+ */
+static void
+enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
+{
+	bool throttled;
+
+	/*
+	 * The code below (indirectly) updates schedutil which looks at
+	 * the cfs_rq utilization to select a frequency.
+	 * Let's add the task's estimated utilization to the cfs_rq's
+	 * estimated utilization, before we update schedutil.
+	 */
+	util_est_enqueue(&rq->cfs, p);
+
+	/*
+	 * If in_iowait is set, the code below may not trigger any cpufreq
+	 * utilization updates, so do it here explicitly with the IOWAIT flag
+	 * passed.
+	 */
+	if (p->in_iowait)
+		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
+
+	throttled = enqueue_entity_fair(rq, &p->se, flags);
+
+	if (!throttled)
 		add_nr_running(rq, 1);
 
 	hrtick_update(rq);
@@ -5044,15 +5052,9 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 
 static void set_next_buddy(struct sched_entity *se);
 
-/*
- * The dequeue_task method is called before nr_running is
- * decreased. We remove the task from the rbtree and
- * update the fair scheduling stats:
- */
-static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
+bool dequeue_entity_fair(struct rq *rq, struct sched_entity *se, int flags)
 {
 	struct cfs_rq *cfs_rq;
-	struct sched_entity *se = &p->se;
 	int task_sleep = flags & DEQUEUE_SLEEP;
 
 	for_each_sched_entity(se) {
@@ -5095,10 +5097,22 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		update_cfs_group(se);
 	}
 
-	if (!se)
+	return se != NULL;
+}
+
+/*
+ * The dequeue_task method is called before nr_running is
+ * decreased. We remove the task from the rbtree and
+ * update the fair scheduling stats:
+ */
+static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
+{
+	bool throttled = dequeue_entity_fair(rq, &p->se, flags);
+
+	if (!throttled)
 		sub_nr_running(rq, 1);
 
-	util_est_dequeue(&rq->cfs, p, task_sleep);
+	util_est_dequeue(&rq->cfs, p, flags & DEQUEUE_SLEEP);
 	hrtick_update(rq);
 }
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3e0ad36938fb..9016049f36c3 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1543,6 +1543,9 @@ extern const u32		sched_prio_to_wmult[40];
 
 #define RETRY_TASK		((void *)-1UL)
 
+bool enqueue_entity_fair(struct rq *rq, struct sched_entity *se, int flags);
+bool dequeue_entity_fair(struct rq *rq, struct sched_entity *se, int flags);
+
 struct sched_class {
 	const struct sched_class *next;
 
-- 
2.9.3.1.gcba166c.dirty