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Subject[PATCH v2 1/6] sched/topology: Store root domain CPU capacity sum
Date
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@arm.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
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