linux-kernel - [PATCH v2 1/6] sched/topology: Store root domain CPU capacity sum

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Message-Id: <20200427083709.30262-2-dietmar.eggemann@arm.com>
Date:   Mon, 27 Apr 2020 10:37:04 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Wei Wang <wvw@...gle.com>, Quentin Perret <qperret@...gle.com>,
        Alessio Balsini <balsini@...gle.com>,
        Pavan Kondeti <pkondeti@...eaurora.org>,
        Patrick Bellasi <patrick.bellasi@...bug.net>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        Qais Yousef <qais.yousef@....com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/6] sched/topology: Store root domain CPU capacity sum

Add sum of (original) CPU capacity of all member CPUs to root domain.

This is needed for capacity-aware SCHED_DEADLINE admission control.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
---
 kernel/sched/sched.h    |  1 +
 kernel/sched/topology.c | 15 +++++++++++----
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index db3a57675ccf..58e1d3903ab9 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -803,6 +803,7 @@ struct root_domain {
 	cpumask_var_t		rto_mask;
 	struct cpupri		cpupri;
 
+	unsigned long           sum_cpu_capacity;
 	unsigned long		max_cpu_capacity;
 
 	/*
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 8344757bba6e..fbb20b7a80c0 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2052,12 +2052,18 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
 	/* Attach the domains */
 	rcu_read_lock();
 	for_each_cpu(i, cpu_map) {
+		unsigned long cap;
+
 		rq = cpu_rq(i);
 		sd = *per_cpu_ptr(d.sd, i);
+		cap = rq->cpu_capacity_orig;
 
 		/* Use READ_ONCE()/WRITE_ONCE() to avoid load/store tearing: */
-		if (rq->cpu_capacity_orig > READ_ONCE(d.rd->max_cpu_capacity))
-			WRITE_ONCE(d.rd->max_cpu_capacity, rq->cpu_capacity_orig);
+		if (cap > READ_ONCE(d.rd->max_cpu_capacity))
+			WRITE_ONCE(d.rd->max_cpu_capacity, cap);
+
+		WRITE_ONCE(d.rd->sum_cpu_capacity,
+			   READ_ONCE(d.rd->sum_cpu_capacity) + cap);
 
 		cpu_attach_domain(sd, d.rd, i);
 	}
@@ -2067,8 +2073,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
 		static_branch_inc_cpuslocked(&sched_asym_cpucapacity);
 
 	if (rq && sched_debug_enabled) {
-		pr_info("root domain span: %*pbl (max cpu_capacity = %lu)\n",
-			cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity);
+		pr_info("root domain span: %*pbl (capacity = %lu max cpu_capacity = %lu)\n",
+			cpumask_pr_args(cpu_map), rq->rd->sum_cpu_capacity,
+			rq->rd->max_cpu_capacity);
 	}
 
 	ret = 0;
-- 
2.17.1