linux-kernel - [PATCH 2/2] sched/fair: Only count group weight for allowed CPUs when looking for dst group

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Message-Id: <20250701024549.40166-3-adamli@os.amperecomputing.com>
Date: Tue,  1 Jul 2025 02:45:49 +0000
From: Adam Li <adamli@...amperecomputing.com>
To: mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org
Cc: dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	vschneid@...hat.com,
	cl@...ux.com,
	linux-kernel@...r.kernel.org,
	patches@...erecomputing.com,
	Adam Li <adamli@...amperecomputing.com>
Subject: [PATCH 2/2] sched/fair: Only count group weight for allowed CPUs when looking for dst group

A task may not use all the CPUs in a schedule group due to CPU affinity.
If group weight includes CPUs not allowed to run the task,
group classification may be incorrect.

Signed-off-by: Adam Li <adamli@...amperecomputing.com>
---
 kernel/sched/fair.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 78a3d9b78e07..452e2df961b9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10722,7 +10722,9 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd,
 
 	sgs->group_capacity = group->sgc->capacity;
 
-	sgs->group_weight = group->group_weight;
+	/* Only count group_weight if p can run on these cpus */
+	sgs->group_weight = cpumask_weight_and(sched_group_span(group),
+				p->cpus_ptr);
 
 	sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
 
-- 
2.34.1