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 <[email protected]> cc: Peter Zijlstra <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> --- kernel/sched/fair.c | 3 +++ kernel/sched/sched.h | 1 + kernel/sched/topology.c | 18 ++++++++++++++++++ 3 files changed, 22 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e497c05aab7f..6116d1b7e441 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6585,6 +6585,9 @@ 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; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 67702b4d9ac7..0fbfbcf5c551 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1153,6 +1153,7 @@ DECLARE_PER_CPU(int, sd_llc_id); DECLARE_PER_CPU(struct sched_domain_shared *, sd_llc_shared); DECLARE_PER_CPU(struct sched_domain *, sd_numa); DECLARE_PER_CPU(struct sched_domain *, sd_asym); +extern struct static_key_false sched_asym_cpucapacity; struct sched_group_capacity { atomic_t ref; diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 61a1125c1ae4..edc87e35fc75 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -398,6 +398,7 @@ DEFINE_PER_CPU(int, sd_llc_id); DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared); DEFINE_PER_CPU(struct sched_domain *, sd_numa); DEFINE_PER_CPU(struct sched_domain *, sd_asym); +DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity); static void update_top_cache_domain(int cpu) { @@ -425,6 +426,21 @@ static void update_top_cache_domain(int cpu) rcu_assign_pointer(per_cpu(sd_asym, 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. @@ -1707,6 +1723,8 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att } rcu_read_unlock(); + update_asym_cpucapacity(cpumask_first(cpu_map)); + 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); -- 2.7.4
