sched/pelt: Cleanup PELT divider

Factorize in a single place the calculation of the divider to be used to
to compute *_avg from *_sum value

Suggested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200612154703.23555-1-vincent.guittot@linaro.org

kernel/sched/fair.c

@@ -3094,7 +3094,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 
 #ifdef CONFIG_SMP
 	do {
-		u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;
+		u32 divider = get_pelt_divider(&se->avg);
 
 		se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
 	} while (0);
@@ -3440,16 +3440,18 @@ static inline void
 update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
 {
 	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
-	/*
-	 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
-	 * See ___update_load_avg() for details.
-	 */
-	u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
+	u32 divider;
 
 	/* Nothing to update */
 	if (!delta)
 		return;
 
+	/*
+	 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
+	 * See ___update_load_avg() for details.
+	 */
+	divider = get_pelt_divider(&cfs_rq->avg);
+
 	/* Set new sched_entity's utilization */
 	se->avg.util_avg = gcfs_rq->avg.util_avg;
 	se->avg.util_sum = se->avg.util_avg * divider;
@@ -3463,16 +3465,18 @@ static inline void
 update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
 {
 	long delta = gcfs_rq->avg.runnable_avg - se->avg.runnable_avg;
-	/*
-	 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
-	 * See ___update_load_avg() for details.
-	 */
-	u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
+	u32 divider;
 
 	/* Nothing to update */
 	if (!delta)
 		return;
 
+	/*
+	 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
+	 * See ___update_load_avg() for details.
+	 */
+	divider = get_pelt_divider(&cfs_rq->avg);
+
 	/* Set new sched_entity's runnable */
 	se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
 	se->avg.runnable_sum = se->avg.runnable_avg * divider;
@@ -3500,7 +3504,7 @@ update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq
 	 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
 	 * See ___update_load_avg() for details.
 	 */
-	divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
+	divider = get_pelt_divider(&cfs_rq->avg);
 
 	if (runnable_sum >= 0) {
 		/*
@@ -3646,7 +3650,7 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
 
 	if (cfs_rq->removed.nr) {
 		unsigned long r;
-		u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
+		u32 divider = get_pelt_divider(&cfs_rq->avg);
 
 		raw_spin_lock(&cfs_rq->removed.lock);
 		swap(cfs_rq->removed.util_avg, removed_util);
@@ -3701,7 +3705,7 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
 	 * cfs_rq->avg.period_contrib can be used for both cfs_rq and se.
 	 * See ___update_load_avg() for details.
 	 */
-	u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
+	u32 divider = get_pelt_divider(&cfs_rq->avg);
 
 	/*
 	 * When we attach the @se to the @cfs_rq, we must align the decay

kernel/sched/pelt.c

@@ -262,7 +262,7 @@ ___update_load_sum(u64 now, struct sched_avg *sa,
 static __always_inline void
 ___update_load_avg(struct sched_avg *sa, unsigned long load)
 {
-	u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
+	u32 divider = get_pelt_divider(sa);
 
 	/*
 	 * Step 2: update *_avg.

kernel/sched/pelt.h

@@ -37,6 +37,11 @@ update_irq_load_avg(struct rq *rq, u64 running)
 }
 #endif
 
+static inline u32 get_pelt_divider(struct sched_avg *avg)
+{
+	return LOAD_AVG_MAX - 1024 + avg->period_contrib;
+}
+
 /*
  * When a task is dequeued, its estimated utilization should not be update if
  * its util_avg has not been updated at least once.