From: Dietmar Eggemann <[email protected]> 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). cc: Ingo Molnar <[email protected]> cc: Peter Zijlstra <[email protected]> Signed-off-by: Dietmar Eggemann <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> --- kernel/sched/core.c | 12 ++++++++++++ kernel/sched/sched.h | 2 ++ 2 files changed, 14 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a0a74b2d9f41..600f1296aa4c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6873,6 +6873,7 @@ 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); @@ -6923,11 +6924,22 @@ 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(rq->rd->max_cpu_capacity)) + WRITE_ONCE(rq->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); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index f44da95c70cd..444d8f38743f 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -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; -- 1.9.1
