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Commit 2929d0b0 authored by Morten Rasmussen's avatar Morten Rasmussen Committed by Satya Durga Srinivasu Prabhala
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FROMLIST: sched: Add static_key for asymmetric cpu capacity optimizations 



The existing asymmetric cpu capacity code should cause minimal overhead
for others. Putting it behind a static_key, it has been done for SMT
optimizations, would make it easier to extend and improve without
causing harm to others moving forward.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>

Change-Id: Iced93ffb71bb2c34eee783c585cffe7252137308
Signed-off-by: default avatarMorten Rasmussen <morten.rasmussen@arm.com>
[Taken from https://lore.kernel.org/lkml/1530699470-29808-2-git-send-email-morten.rasmussen@arm.com

]
Signed-off-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Signed-off-by: default avatarChris Redpath <chris.redpath@arm.com>
Git-commit: 83a9ce05
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: default avatarPuja Gupta <pujag@codeaurora.org>
parent d18a2e31

kernel/sched/fair.c

+3 −0
Original line number Diff line number Diff line
@@ -7523,6 +7523,9 @@ static int wake_cap(struct task_struct *p, int cpu, int prev_cpu) 
{

	long min_cap, max_cap;



	if (!static_branch_unlikely(&sched_asym_cpucapacity))

		return 0;



	min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));

	max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;

kernel/sched/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -1190,6 +1190,7 @@ DECLARE_PER_CPU(struct sched_domain *, sd_numa); 
DECLARE_PER_CPU(struct sched_domain *, sd_asym);

DECLARE_PER_CPU(struct sched_domain *, sd_ea);

DECLARE_PER_CPU(struct sched_domain *, sd_scs);

extern struct static_key_false sched_asym_cpucapacity;



struct sched_group_capacity {

	atomic_t ref;

kernel/sched/topology.c

+19 −0
Original line number Diff line number Diff line
@@ -418,6 +418,7 @@ DEFINE_PER_CPU(struct sched_domain *, sd_numa); 
DEFINE_PER_CPU(struct sched_domain *, sd_asym);

DEFINE_PER_CPU(struct sched_domain *, sd_ea);

DEFINE_PER_CPU(struct sched_domain *, sd_scs);

DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);



static void update_top_cache_domain(int cpu)

{
@@ -457,6 +458,21 @@ static void update_top_cache_domain(int cpu) 
	rcu_assign_pointer(per_cpu(sd_scs, cpu), sd);

}



static void update_asym_cpucapacity(int cpu)

{

	int enable = false;



	rcu_read_lock();

	if (lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY))

		enable = true;

	rcu_read_unlock();



	if (enable) {

		/* This expects to be hotplug-safe */

		static_branch_enable_cpuslocked(&sched_asym_cpucapacity);

	}

}



/*

 * Attach the domain 'sd' to 'cpu' as its base domain. Callers must

 * hold the hotplug lock.
@@ -1868,6 +1884,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att 
	}

	rcu_read_unlock();



	if (!cpumask_empty(cpu_map))

		update_asym_cpucapacity(cpumask_first(cpu_map));



	if (rq && sched_debug_enabled) {

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

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