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

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  Re: [RFCv5 PATCH 16/46] sched: Allocate and initialize energy data  structures Peter Zijlstra <peterz@infradead.org> - 2015-08-12 12:20 +0200
    Re: [RFCv5 PATCH 16/46] sched: Allocate and initialize energy data  structures Dietmar Eggemann <dietmar.eggemann@arm.com> - 2015-08-12 19:20 +0200
      Re: [RFCv5 PATCH 16/46] sched: Allocate and initialize energy data  structures Peter Zijlstra <peterz@infradead.org> - 2015-08-12 19:30 +0200

#1205894 — 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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#1206285

On 12/08/15 11:17, Peter Zijlstra wrote:
> 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)

[...]

>> @@ -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?
> 

Yeah, that's not strictly necessary. I could get rid of all the
allocation/copying/ and freeing code and just simply set sd->groups->sge
= fn(cpu) in init_sched_energy(). Plus delete the atomic_t ref in struct
sched_group_energy.

In this case, should I still keep the check_sched_energy_data() function
to verify that the scheduler got valid data via the struct
sched_domain_topology_level table from the arch, i.e. to make sure that
the per-cpu provided sd energy data is consistent for all cpus within
the sched group cpumask?

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#1206291

On Wed, Aug 12, 2015 at 06:09:59PM +0100, Dietmar Eggemann wrote:
> > One more question, if fn() returns a full structure, why are we
> > allocating and copying the thing? Its all const read only data, right?
> > 
> 
> Yeah, that's not strictly necessary. I could get rid of all the
> allocation/copying/ and freeing code and just simply set sd->groups->sge
> = fn(cpu) in init_sched_energy(). Plus delete the atomic_t ref in struct
> sched_group_energy.
> 
> In this case, should I still keep the check_sched_energy_data() function
> to verify that the scheduler got valid data via the struct
> sched_domain_topology_level table from the arch, i.e. to make sure that
> the per-cpu provided sd energy data is consistent for all cpus within
> the sched group cpumask?

Oh yes very much. We want sanity checking of the data handed.
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