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Commit cd92bfd3 authored by Dietmar Eggemann's avatar Dietmar Eggemann Committed by Ingo Molnar
Browse files

sched/core: Store maximum per-CPU capacity in root domain 



To be able to compare the capacity of the target CPU with the highest
available CPU capacity, store the maximum per-CPU capacity in the root
domain.

The max per-CPU capacity should be 1024 for all systems except SMT,
where the capacity is currently based on smt_gain and the number of
hardware threads and is <1024. If SMT can be brought to work with a
per-thread capacity of 1024, this patch can be dropped and replaced by a
hard-coded max capacity of 1024 (=SCHED_CAPACITY_SCALE).

Signed-off-by: default avatarDietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: default avatarMorten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: freedom.tan@mediatek.com
Cc: keita.kobayashi.ym@renesas.com
Cc: mgalbraith@suse.de
Cc: sgurrappadi@nvidia.com
Cc: vincent.guittot@linaro.org
Cc: yuyang.du@intel.com
Link: http://lkml.kernel.org/r/26c69258-9947-f830-a53e-0c54e7750646@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9ee1cda5

kernel/sched/core.c

+12 −0
Original line number Diff line number Diff line
@@ -6903,6 +6903,7 @@ static int build_sched_domains(const struct cpumask *cpu_map, 
	enum s_alloc alloc_state;

	struct sched_domain *sd;

	struct s_data d;

	struct rq *rq = NULL;

	int i, ret = -ENOMEM;



	alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
@@ -6953,11 +6954,22 @@ static int build_sched_domains(const struct cpumask *cpu_map, 
	/* Attach the domains */

	rcu_read_lock();

	for_each_cpu(i, cpu_map) {

		rq = cpu_rq(i);

		sd = *per_cpu_ptr(d.sd, i);



		/* 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);



		cpu_attach_domain(sd, d.rd, i);

	}

	rcu_read_unlock();



	if (rq) {

		pr_info("span: %*pbl (max cpu_capacity = %lu)\n",

			cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity);

	}



	ret = 0;

error:

	__free_domain_allocs(&d, alloc_state, cpu_map);

kernel/sched/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -565,6 +565,8 @@ struct root_domain { 
	 */

	cpumask_var_t rto_mask;

	struct cpupri cpupri;



	unsigned long max_cpu_capacity;

};



extern struct root_domain def_root_domain;