linux-kernel - Re: [RFCv5 PATCH 16/46] sched: Allocate and initialize energy data structures

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Date:	Wed, 12 Aug 2015 12:17:21 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	mingo@...hat.com, vincent.guittot@...aro.org,
	daniel.lezcano@...aro.org,
	Dietmar Eggemann <Dietmar.Eggemann@....com>,
	yuyang.du@...el.com, mturquette@...libre.com, rjw@...ysocki.net,
	Juri Lelli <Juri.Lelli@....com>, sgurrappadi@...dia.com,
	pang.xunlei@....com.cn, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [RFCv5 PATCH 16/46] sched: Allocate and initialize energy data
 structures

On Tue, Jul 07, 2015 at 07:23:59PM +0100, Morten Rasmussen wrote:
> @@ -6647,10 +6703,24 @@ static int __sdt_alloc(const struct cpumask *cpu_map)
>  		if (!sdd->sgc)
>  			return -ENOMEM;
>  
> +		sdd->sge = alloc_percpu(struct sched_group_energy *);
> +		if (!sdd->sge)
> +			return -ENOMEM;
> +
>  		for_each_cpu(j, cpu_map) {
>  			struct sched_domain *sd;
>  			struct sched_group *sg;
>  			struct sched_group_capacity *sgc;
> +			struct sched_group_energy *sge;
> +			sched_domain_energy_f fn = tl->energy;
> +			unsigned int nr_idle_states = 0;
> +			unsigned int nr_cap_states = 0;
> +
> +			if (fn && fn(j)) {
> +				nr_idle_states = fn(j)->nr_idle_states;
> +				nr_cap_states = fn(j)->nr_cap_states;
> +				BUG_ON(!nr_idle_states || !nr_cap_states);
> +			}
>  
>  		       	sd = kzalloc_node(sizeof(struct sched_domain) + cpumask_size(),
>  					GFP_KERNEL, cpu_to_node(j));
> @@ -6674,6 +6744,16 @@ static int __sdt_alloc(const struct cpumask *cpu_map)
>  				return -ENOMEM;
>  
>  			*per_cpu_ptr(sdd->sgc, j) = sgc;
> +
> +			sge = kzalloc_node(sizeof(struct sched_group_energy) +
> +				nr_idle_states*sizeof(struct idle_state) +
> +				nr_cap_states*sizeof(struct capacity_state),
> +				GFP_KERNEL, cpu_to_node(j));
> +
> +			if (!sge)
> +				return -ENOMEM;
> +
> +			*per_cpu_ptr(sdd->sge, j) = sge;
>  		}
>  	}
>  

One more question, if fn() returns a full structure, why are we
allocating and copying the thing? Its all const read only data, right?

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