linux-kernel - [tip: sched/core] sched/fair: Simplify the work when reweighting entity

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Date:   Thu, 27 Aug 2020 07:54:32 -0000
From:   "tip-bot2 for Jiang Biao" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Jiang Biao <benbjiang@...cent.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: sched/core] sched/fair: Simplify the work when reweighting entity

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     1724b95b92979a8ea8e55a4817d05b3bb7750958
Gitweb:        https://git.kernel.org/tip/1724b95b92979a8ea8e55a4817d05b3bb7750958
Author:        Jiang Biao <benbjiang@...cent.com>
AuthorDate:    Tue, 11 Aug 2020 19:32:09 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 26 Aug 2020 12:41:58 +02:00

sched/fair: Simplify the work when reweighting entity

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 <benbjiang@...cent.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
Link: https://lkml.kernel.org/r/20200811113209.34057-1-benbjiang@tencent.com
---
 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 90ebaa4..33699db 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3084,7 +3084,7 @@ 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);
 
@@ -3100,7 +3100,7 @@ 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);
 
 }