[PATCH v3] sched/fair: simplfy the work when reweighting entity

[Jiang Biao]

From: Jiang Biao <benbji...@tencent.com>

The code in reweight_entity() can be simplified.

For a sched entity on the rq, the entity accounting can be replaced by
cfs_rq instantaneous load updates currently called from within the
entity accounting.

Even though an entity on the rq can't represent a task in
reweight_entity() (a task is always dequeued before calling this
function) and so the numa task accounting and the rq->cfs_tasks list
management of the entity accounting are never called, the redundant
cfs_rq->nr_running decrement/increment will be avoided.

Signed-off-by: Jiang Biao <benbji...@tencent.com>
---
v3<-v2: Amend commit log taking Dietmar's advice. Thx.
v2<-v1: Amend the commit log

 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 04fa8dbcfa4d..18a8fc7bd0de 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3086,7 +3086,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct 
sched_entity *se,
                /* commit outstanding execution time */
                if (cfs_rq->curr == se)
                        update_curr(cfs_rq);
-               account_entity_dequeue(cfs_rq, se);
+               update_load_sub(&cfs_rq->load, se->load.weight);
        }
        dequeue_load_avg(cfs_rq, se);
 
@@ -3102,7 +3102,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct 
sched_entity *se,
 
        enqueue_load_avg(cfs_rq, se);
        if (se->on_rq)
-               account_entity_enqueue(cfs_rq, se);
+               update_load_add(&cfs_rq->load, se->load.weight);
 
 }
 
-- 
2.21.0