linux-kernel - [PATCH 5/7] sched/topology: Remove CPUs with NULL sd from HKR_TYPE

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Date: Wed,  3 Apr 2024 17:05:37 +0200
From: Pierre Gondois <pierre.gondois@....com>
To: linux-kernel@...r.kernel.org
Cc: Aaron Lu <aaron.lu@...el.com>,
	Rui Zhang <rui.zhang@...el.com>,
	Pierre Gondois <pierre.gondois@....com>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Frederic Weisbecker <frederic@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Tejun Heo <tj@...nel.org>,
	Michal Hocko <mhocko@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Waiman Long <longman@...hat.com>
Subject: [PATCH 5/7] sched/topology: Remove CPUs with NULL sd from HKR_TYPE_SCHED mask

Upon attaching a NULL sched domain to a CPU, remove the CPU from
the HKR_TYPE_SCHED isolation mask. CPUs present in this mask
are prevented from being added to the fair.c variables:
- nohz.idle_cpus_mask
- nohz.nr_cpus

Signed-off-by: Pierre Gondois <pierre.gondois@....com>
---
 kernel/sched/topology.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 63aecd2a7a9f..b4fc212ccfb0 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -775,6 +775,11 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
 
 	sched_domain_debug(sd, cpu);
 
+	if (sd)
+		housekeeping_runtime_set_cpu(cpu, HKR_TYPE_SCHED);
+	else
+		housekeeping_runtime_clear_cpu(cpu, HKR_TYPE_SCHED);
+
 	rq_attach_root(rq, rd);
 	tmp = rq->sd;
 	rcu_assign_pointer(rq->sd, sd);
-- 
2.25.1