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

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Date:	Thu, 11 Sep 2014 16:06:06 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Vincent Guittot <vincent.guittot@...aro.org>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, linux@....linux.org.uk,
	linux-arm-kernel@...ts.infradead.org, riel@...hat.com,
	Morten.Rasmussen@....com, efault@....de, nicolas.pitre@...aro.org,
	linaro-kernel@...ts.linaro.org, daniel.lezcano@...aro.org,
	dietmar.eggemann@....com
Subject: Re: [PATCH v5 04/12] sched: Allow all archs to set the capacity_orig

On 09/10/2014 07:20 PM, Peter Zijlstra 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.
> 
> 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;
> 
> 
Alright, I see now. Thanks!

Regards
Preeti U Murthy

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