sched/pelt: Sync util/runnable_sum with PELT window when propagating

update_tg_cfs_*() propagate the impact of the attach/detach of an entity
down into the cfs_rq hierarchy and must keep the sync with the current pelt
window.

Even if we can't sync child cfs_rq and its group se, we can sync the group
se and its parent cfs_rq with current position in the PELT window. In fact,
we must keep them sync in order to stay also synced with others entities
and group entities that are already attached to the cfs_rq.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200506155301.14288-1-vincent.guittot@linaro.org

1 files changed, 27 insertions, 22 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4e586863827b..44b0c8edc260 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3441,52 +3441,46 @@ 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;
 
 	/* Nothing to update */
 	if (!delta)
 		return;
 
-	/*
-	 * The relation between sum and avg is:
-	 *
-	 *   LOAD_AVG_MAX - 1024 + sa->period_contrib
-	 *
-	 * however, the PELT windows are not aligned between grq and gse.
-	 */
-
 	/* Set new sched_entity's utilization */
 	se->avg.util_avg = gcfs_rq->avg.util_avg;
-	se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;
+	se->avg.util_sum = se->avg.util_avg * divider;
 
 	/* Update parent cfs_rq utilization */
 	add_positive(&cfs_rq->avg.util_avg, delta);
-	cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
+	cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
 }
 
 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;
 
 	/* Nothing to update */
 	if (!delta)
 		return;
 
-	/*
-	 * The relation between sum and avg is:
-	 *
-	 *   LOAD_AVG_MAX - 1024 + sa->period_contrib
-	 *
-	 * however, the PELT windows are not aligned between grq and gse.
-	 */
-
 	/* Set new sched_entity's runnable */
 	se->avg.runnable_avg = gcfs_rq->avg.runnable_avg;
-	se->avg.runnable_sum = se->avg.runnable_avg * LOAD_AVG_MAX;
+	se->avg.runnable_sum = se->avg.runnable_avg * divider;
 
 	/* Update parent cfs_rq runnable */
 	add_positive(&cfs_rq->avg.runnable_avg, delta);
-	cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * LOAD_AVG_MAX;
+	cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;
 }
 
 static inline void
@@ -3496,19 +3490,26 @@ update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq
 	unsigned long load_avg;
 	u64 load_sum = 0;
 	s64 delta_sum;
+	u32 divider;
 
 	if (!runnable_sum)
 		return;
 
 	gcfs_rq->prop_runnable_sum = 0;
 
+	/*
+	 * 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;
+
 	if (runnable_sum >= 0) {
 		/*
 		 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
 		 * the CPU is saturated running == runnable.
 		 */
 		runnable_sum += se->avg.load_sum;
-		runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
+		runnable_sum = min_t(long, runnable_sum, divider);
 	} else {
 		/*
 		 * Estimate the new unweighted runnable_sum of the gcfs_rq by
@@ -3533,7 +3534,7 @@ update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq
 	runnable_sum = max(runnable_sum, running_sum);
 
 	load_sum = (s64)se_weight(se) * runnable_sum;
-	load_avg = div_s64(load_sum, LOAD_AVG_MAX);
+	load_avg = div_s64(load_sum, divider);
 
 	delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
 	delta_avg = load_avg - se->avg.load_avg;
@@ -3697,6 +3698,10 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
  */
 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
+	/*
+	 * 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;
 
 	/*