linux-kernel - Re: [PATCH v2 06/13] sched: Store maximum per-cpu capacity in root domain

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Date:	Wed, 13 Jul 2016 14:40:14 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Yuyang Du <yuyang.du@...el.com>, mgalbraith@...e.de,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 06/13] sched: Store maximum per-cpu capacity in root domain

On 22 June 2016 at 19:03, Morten Rasmussen <morten.rasmussen@....com> wrote:
> From: Dietmar Eggemann <dietmar.eggemann@....com>
>
> 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.

I thought that the capacity of all CPUS were built so the highest
capacity of the CPU of the system is 1024  for big LITTLE system . So
this patch doesn't seem necessary for big.LITTLE system

>
> cc: Ingo Molnar <mingo@...hat.com>
> cc: Peter Zijlstra <peterz@...radead.org>
>
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
> Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
> ---
>  kernel/sched/core.c  | 9 +++++++++
>  kernel/sched/sched.h | 2 ++
>  2 files changed, 11 insertions(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index fe39118ffdfb..5093765e9930 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6855,6 +6855,7 @@ 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);
> @@ -6905,11 +6906,19 @@ 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);
>                 cpu_attach_domain(sd, d.rd, i);
> +
> +               if (rq->cpu_capacity_orig > rq->rd->max_cpu_capacity)
> +                       rq->rd->max_cpu_capacity = rq->cpu_capacity_orig;
>         }
>         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 72f1f3087b04..3e9904ef224f 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -564,6 +564,8 @@ 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
>