[PATCH 3/6 v5] sched: factorize PELT update

[Vincent Guittot]

Every time, we modify load/utilization of sched_entity, we start to sync
it with its cfs_rq. This update is done is different ways:
-when attaching/detaching a sched_entity, we update cfs_rq and then we
sync the entity with the cfs_rq.
-when enqueueing/dequeuing the sched_entity, we update both sched_entity
and cfs_rq metrics to now.

Use update_load_avg everytime we have to update and sync cfs_rq and
sched_entity before changing the state of a sched_enity

Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 kernel/sched/fair.c | 75 +++++++++++++++++------------------------------------
 1 file changed, 24 insertions(+), 51 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ecc66d6..52cbc92 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3098,8 +3098,14 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
 	return decayed || removed_load;
 }
 
+/*
+ * Optional action to be done while updating the load average
+ */
+#define UPDATE_TG	0x1
+#define SKIP_AGE_LOAD	0x2
+
 /* Update task and its cfs_rq load average */
-static inline void update_load_avg(struct sched_entity *se, int update_tg)
+static inline void update_load_avg(struct sched_entity *se, int flags)
 {
 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 	u64 now = cfs_rq_clock_task(cfs_rq);
@@ -3110,11 +3116,12 @@ static inline void update_load_avg(struct sched_entity *se, int update_tg)
 	 * Track task load average for carrying it to new CPU after migrated, and
 	 * track group sched_entity load average for task_h_load calc in migration
 	 */
-	__update_load_avg(now, cpu, &se->avg,
+	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
+		__update_load_avg(now, cpu, &se->avg,
 			  se->on_rq * scale_load_down(se->load.weight),
 			  cfs_rq->curr == se, NULL);
 
-	if (update_cfs_rq_load_avg(now, cfs_rq, true) && update_tg)
+	if (update_cfs_rq_load_avg(now, cfs_rq, true) && (flags & UPDATE_TG))
 		update_tg_load_avg(cfs_rq, 0);
 }
 
@@ -3128,26 +3135,6 @@ static inline void update_load_avg(struct sched_entity *se, int update_tg)
  */
 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-	if (!sched_feat(ATTACH_AGE_LOAD))
-		goto skip_aging;
-
-	/*
-	 * If we got migrated (either between CPUs or between cgroups) we'll
-	 * have aged the average right before clearing @last_update_time.
-	 *
-	 * Or we're fresh through post_init_entity_util_avg().
-	 */
-	if (se->avg.last_update_time) {
-		__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
-				  &se->avg, 0, 0, NULL);
-
-		/*
-		 * XXX: we could have just aged the entire load away if we've been
-		 * absent from the fair class for too long.
-		 */
-	}
-
-skip_aging:
 	se->avg.last_update_time = cfs_rq->avg.last_update_time;
 	cfs_rq->avg.load_avg += se->avg.load_avg;
 	cfs_rq->avg.load_sum += se->avg.load_sum;
@@ -3167,9 +3154,6 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
  */
 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-	__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
-			  &se->avg, se->on_rq * scale_load_down(se->load.weight),
-			  cfs_rq->curr == se, NULL);
 
 	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
 	sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
@@ -3184,34 +3168,20 @@ static inline void
 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
 	struct sched_avg *sa = &se->avg;
-	u64 now = cfs_rq_clock_task(cfs_rq);
-	int migrated, decayed;
-
-	migrated = !sa->last_update_time;
-	if (!migrated) {
-		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
-			se->on_rq * scale_load_down(se->load.weight),
-			cfs_rq->curr == se, NULL);
-	}
-
-	decayed = update_cfs_rq_load_avg(now, cfs_rq, !migrated);
 
 	cfs_rq->runnable_load_avg += sa->load_avg;
 	cfs_rq->runnable_load_sum += sa->load_sum;
 
-	if (migrated)
+	if (!sa->last_update_time) {
 		attach_entity_load_avg(cfs_rq, se);
-
-	if (decayed || migrated)
 		update_tg_load_avg(cfs_rq, 0);
+	}
 }
 
 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
 static inline void
 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
-	update_load_avg(se, 1);
-
 	cfs_rq->runnable_load_avg =
 		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
 	cfs_rq->runnable_load_sum =
@@ -3285,7 +3255,10 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
 	return 0;
 }
 
-static inline void update_load_avg(struct sched_entity *se, int not_used)
+#define UPDATE_TG	0x0
+#define SKIP_AGE_LOAD	0x0
+
+static inline void update_load_avg(struct sched_entity *se, int not_used1)
 {
 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 	struct rq *rq = rq_of(cfs_rq);
@@ -3433,6 +3406,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 	if (renorm && !curr)
 		se->vruntime += cfs_rq->min_vruntime;
 
+	update_load_avg(se, UPDATE_TG);
 	enqueue_entity_load_avg(cfs_rq, se);
 	account_entity_enqueue(cfs_rq, se);
 	update_cfs_shares(cfs_rq);
@@ -3507,6 +3481,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 	 * Update run-time statistics of the 'current'.
 	 */
 	update_curr(cfs_rq);
+	update_load_avg(se, UPDATE_TG);
 	dequeue_entity_load_avg(cfs_rq, se);
 
 	update_stats_dequeue(cfs_rq, se, flags);
@@ -3594,7 +3569,7 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 		 */
 		update_stats_wait_end(cfs_rq, se);
 		__dequeue_entity(cfs_rq, se);
-		update_load_avg(se, 1);
+		update_load_avg(se, UPDATE_TG);
 	}
 
 	update_stats_curr_start(cfs_rq, se);
@@ -3712,7 +3687,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 	/*
 	 * Ensure that runnable average is periodically updated.
 	 */
-	update_load_avg(curr, 1);
+	update_load_avg(curr, UPDATE_TG);
 	update_cfs_shares(cfs_rq);
 
 #ifdef CONFIG_SCHED_HRTICK
@@ -4601,7 +4576,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		if (cfs_rq_throttled(cfs_rq))
 			break;
 
-		update_load_avg(se, 1);
+		update_load_avg(se, UPDATE_TG);
 		update_cfs_shares(cfs_rq);
 	}
 
@@ -4660,7 +4635,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		if (cfs_rq_throttled(cfs_rq))
 			break;
 
-		update_load_avg(se, 1);
+		update_load_avg(se, UPDATE_TG);
 		update_cfs_shares(cfs_rq);
 	}
 
@@ -8715,7 +8690,6 @@ static void detach_task_cfs_rq(struct task_struct *p)
 {
 	struct sched_entity *se = &p->se;
 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
-	u64 now = cfs_rq_clock_task(cfs_rq);
 
 	if (!vruntime_normalized(p)) {
 		/*
@@ -8727,7 +8701,7 @@ static void detach_task_cfs_rq(struct task_struct *p)
 	}
 
 	/* Catch up with the cfs_rq and remove our load when we leave */
-	update_cfs_rq_load_avg(now, cfs_rq, false);
+	update_load_avg(se, 0);
 	detach_entity_load_avg(cfs_rq, se);
 	update_tg_load_avg(cfs_rq, false);
 }
@@ -8735,7 +8709,6 @@ static void detach_task_cfs_rq(struct task_struct *p)
 static void attach_entity_cfs_rq(struct sched_entity *se)
 {
 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
-	u64 now = cfs_rq_clock_task(cfs_rq);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 	/*
@@ -8746,7 +8719,7 @@ static void attach_entity_cfs_rq(struct sched_entity *se)
 #endif
 
 	/* Synchronize entity with its cfs_rq */
-	update_cfs_rq_load_avg(now, cfs_rq, false);
+	update_load_avg(se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
 	attach_entity_load_avg(cfs_rq, se);
 	update_tg_load_avg(cfs_rq, false);
 }
-- 
2.7.4