linux-kernel - Re: [PATCH v5 04/12] sched: Allow all archs to set the capacity

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Date:	Wed, 10 Sep 2014 16:22:12 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	Rik van Riel <riel@...hat.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Mike Galbraith <efault@....de>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v5 04/12] sched: Allow all archs to set the capacity_orig

On 10 September 2014 15:50, Peter Zijlstra <peterz@...radead.org> wrote:
> On Sat, Aug 30, 2014 at 10:37:40PM +0530, Preeti U Murthy wrote:
>> > -   if ((sd->flags & SD_SHARE_CPUCAPACITY) && weight > 1) {
>> > -           if (sched_feat(ARCH_CAPACITY))
>>
>> Aren't you missing this check above? I understand that it is not
>> crucial, but that would also mean removing ARCH_CAPACITY sched_feat
>> altogether, wouldn't it?
>
> Yes he's missing that, I added the below bit on top.

FWIW, your changes are fine for me

>
> So the argument last time:
> lkml.kernel.org/r/20140709105721.GT19379@...ns.programming.kicks-ass.net
> was that you cannot put sched_feat(ARCH_CAPACITY) inside a weak arch_*
> function. The test has to be outside, seeing how it needs to decide to
> call the arch function at all (or revert to the default implementation).
>
> ---
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5700,7 +5700,7 @@ unsigned long __weak arch_scale_freq_cap
>         return default_scale_capacity(sd, cpu);
>  }
>
> -unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
> +static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
>  {
>         if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
>                 return sd->smt_gain / sd->span_weight;
> @@ -5708,6 +5708,11 @@ unsigned long __weak arch_scale_cpu_capa
>         return SCHED_CAPACITY_SCALE;
>  }
>
> +unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
> +{
> +       return default_scale_cpu_capacity(sd, cpu);
> +}
> +
>  static unsigned long scale_rt_capacity(int cpu)
>  {
>         struct rq *rq = cpu_rq(cpu);
> @@ -5747,7 +5752,10 @@ static void update_cpu_capacity(struct s
>         unsigned long capacity = SCHED_CAPACITY_SCALE;
>         struct sched_group *sdg = sd->groups;
>
> -       capacity *= arch_scale_cpu_capacity(sd, cpu);
> +       if (sched_feat(ARCH_CAPACITY))
> +               capacity *= arch_scale_cpu_capacity(sd, cpu);
> +       else
> +               capacity *= default_scale_cpu_capacity(sd, cpu);
>
>         capacity >>= SCHED_CAPACITY_SHIFT;
>
--
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