linux-kernel - [PATCH 1/2] sched/fair: Decrease cfs bandwidth usage in task

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Message-Id: <20240721125208.5348-2-zhouchuyi@bytedance.com>
Date: Sun, 21 Jul 2024 20:52:07 +0800
From: Chuyi Zhou <zhouchuyi@...edance.com>
To: mingo@...hat.com,
	peterz@...radead.org,
	juri.lelli@...hat.com,
	vincent.guittot@...aro.org,
	dietmar.eggemann@....com,
	rostedt@...dmis.org,
	bsegall@...gle.com,
	mgorman@...e.de,
	vschneid@...hat.com
Cc: chengming.zhou@...ux.dev,
	linux-kernel@...r.kernel.org,
	joshdon@...gle.com,
	Chuyi Zhou <zhouchuyi@...edance.com>
Subject: [PATCH 1/2] sched/fair: Decrease cfs bandwidth usage in task_group destruction

The static key __cfs_bandwidth_used is used to indicate whether bandwidth
control is enabled in the system. Currently, it is only decreased when a
task group disables bandwidth control. This is incorrect because if there
was a task group in the past that enabled bandwidth control, the
__cfs_bandwidth_used will never go to zero, even if there are no task_group
using bandwidth control now.

This patch tries to fix this issue by decrsasing bandwidth usage in
destroy_cfs_bandwidth().

Signed-off-by: Chuyi Zhou <zhouchuyi@...edance.com>
---
 kernel/sched/fair.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b1e07ce90284..7ad50dc31a93 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6447,6 +6447,9 @@ static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
 	hrtimer_cancel(&cfs_b->period_timer);
 	hrtimer_cancel(&cfs_b->slack_timer);
 
+	if (cfs_b->quota != RUNTIME_INF)
+		cfs_bandwidth_usage_dec();
+
 	/*
 	 * It is possible that we still have some cfs_rq's pending on a CSD
 	 * list, though this race is very rare. In order for this to occur, we
-- 
2.20.1