linux-kernel - [PATCH] sched/fair: Sync se's load_avg with cfs_rq in reweight

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Message-Id: <20240716150840.23061-1-zhouchuyi@bytedance.com>
Date: Tue, 16 Jul 2024 23:08:40 +0800
From: Chuyi Zhou <zhouchuyi@...edance.com>
To: mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org
Cc: chengming.zhou@...ux.dev,
	linux-kernel@...r.kernel.org,
	Chuyi Zhou <zhouchuyi@...edance.com>
Subject: [PATCH] sched/fair: Sync se's load_avg with cfs_rq in reweight_entity

In reweight_entity(), if !se->on_rq (e.g. when we are reweighting a
sleeping task), we should sync the load_avg of se to cfs_rq before calling
dequeue_load_avg(). Otherwise, the load_avg of this se can be inaccurate.

Signed-off-by: Chuyi Zhou <zhouchuyi@...edance.com>
---
 kernel/sched/fair.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9057584ec06d..2807f6e72ad1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3782,6 +3782,8 @@ static void reweight_eevdf(struct sched_entity *se, u64 avruntime,
 	se->deadline = avruntime + vslice;
 }
 
+static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags);
+
 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 			    unsigned long weight)
 {
@@ -3795,7 +3797,11 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 		if (!curr)
 			__dequeue_entity(cfs_rq, se);
 		update_load_sub(&cfs_rq->load, se->load.weight);
+	} else {
+		/* Sync with the cfs_rq before removing our load_avg */
+		update_load_avg(cfs_rq, se, 0);
 	}
+
 	dequeue_load_avg(cfs_rq, se);
 
 	if (se->on_rq) {
-- 
2.20.1