[PATCH v4 2/3] sched/fair: split the remove_entity_load_avg() into two functions

[byungchul.park]

From: Byungchul Park <byungchul.park@xxxxxxx>

remove_entity_load_avg() consists of two parts. the first part is for
updating se's last_update_time and the second part is for removing
se's load from cfs_rq. it can become necessary to use only the first
part or second part, for the purpose of optimization. so this patch
splits this function into two other functions.

additionally, remove_entity_load_avg() is performed with a se and the
se's current cfs_rq, mostly. however it can become necessary to
perform it with a se and previous cfs_rq during migration for the
purpose of optimization. so this patch adds another a agument, that
is, cfs_rq to remove_entity_load_avg().

Signed-off-by: Byungchul Park <byungchul.park@xxxxxxx>
---
 kernel/sched/fair.c |   31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e9c5668..522aa07 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2853,13 +2853,9 @@ void set_task_rq_fair(struct sched_entity *se,
 }
 #endif
 
-/*
- * Task first catches up with cfs_rq, and then subtract
- * itself from the cfs_rq (task must be off the queue now).
- */
-void remove_entity_load_avg(struct sched_entity *se)
+/* This is useful when rq lock may not be held */
+static inline void __update_entity_load_avg(struct sched_entity *se, struct cfs_rq *cfs_rq)
 {
-	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 	u64 last_update_time;
 
 #ifndef CONFIG_64BIT
@@ -2875,11 +2871,25 @@ void remove_entity_load_avg(struct sched_entity *se)
 #endif
 
 	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
+}
+
+static inline void __remove_entity_load_avg(struct sched_entity *se, struct cfs_rq *cfs_rq)
+{
 	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
 	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
 }
 
 /*
+ * Task first catches up with cfs_rq, and then subtract
+ * itself from the cfs_rq (task must be off the queue now).
+ */
+static inline void remove_entity_load_avg(struct sched_entity *se, struct cfs_rq *cfs_rq)
+{
+	__update_entity_load_avg(se, cfs_rq);
+	__remove_entity_load_avg(se, cfs_rq);
+}
+
+/*
  * Update the rq's load with the elapsed running time before entering
  * idle. if the last scheduled task is not a CFS task, idle_enter will
  * be the only way to update the runnable statistic.
@@ -2916,7 +2926,8 @@ static inline void
 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
 static inline void
 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
-static inline void remove_entity_load_avg(struct sched_entity *se) {}
+static inline void
+remove_entity_load_avg(struct sched_entity *se, struct cfs_rq *cfs_rq) {}
 
 static inline void
 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
@@ -5063,7 +5074,7 @@ static void migrate_task_rq_fair(struct task_struct *p, int next_cpu)
 	 * will result in the wakee task is less decayed, but giving the wakee more
 	 * load sounds not bad.
 	 */
-	remove_entity_load_avg(&p->se);
+	remove_entity_load_avg(&p->se, cfs_rq_of(&p->se));
 
 	/* Tell new CPU we are migrated */
 	p->se.avg.last_update_time = 0;
@@ -5074,7 +5085,7 @@ static void migrate_task_rq_fair(struct task_struct *p, int next_cpu)
 
 static void task_dead_fair(struct task_struct *p)
 {
-	remove_entity_load_avg(&p->se);
+	remove_entity_load_avg(&p->se, cfs_rq_of(&p->se));
 }
 #endif /* CONFIG_SMP */
 
@@ -8144,7 +8155,7 @@ void free_fair_sched_group(struct task_group *tg)
 			kfree(tg->cfs_rq[i]);
 		if (tg->se) {
 			if (tg->se[i])
-				remove_entity_load_avg(tg->se[i]);
+				remove_entity_load_avg(tg->se[i], cfs_rq_of(tg->se[i]));
 			kfree(tg->se[i]);
 		}
 	}
-- 
1.7.9.5

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