linux-kernel - Re: [PATCH v2 05/11] ARM: topology: use new cpu

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Message-ID: <53830707.5020001@linux.vnet.ibm.com>
Date:	Mon, 26 May 2014 14:49:03 +0530
From:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	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>,
	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>
Subject: Re: [PATCH v2 05/11] ARM: topology: use new cpu_power interface

On 05/26/2014 01:55 PM, Vincent Guittot wrote:
> On 25 May 2014 15:22, Preeti U Murthy <preeti@...ux.vnet.ibm.com> wrote:
>> Hi Vincent,
>>
>> Why do we have two interfaces arch_scale_freq_power() and
>> arch_scale_cpu_power()? Does it make sense to consolidate them now ?
> Hi Preeti,
> 
> They don't have the same purpose. arch_scale_cpu_power set the max
> capacity of your CPU whereas arch_scale_freq_power can be used to give
> the current capacity. ARM platform were using arch_scale_freq_power
> because it was the only one available for non SMT system but this
> induces some misunderstanding and some limitation in the
> characterization of a CPUs. This consolidation is a necessary step so
> we can now have the max capacity of a CPU and let
> arch_scale_freq_power for other purpose (or even remove it if
> useless).

Ah ok! Thanks :) This was insightful :)

Regards
Preeti U Murthy
> 
> Regards,
> Vincent
> 
>>
>> Regards
>> Preeti U Murthy
>>
>>
>> On 05/23/2014 09:22 PM, Vincent Guittot wrote:
>>> Use the new arch_scale_cpu_power in order to reflect the original capacity of
>>> a CPU instead of arch_scale_freq_power which is more linked to a scaling of
>>> the capacity linked to the frequency.
>>>
>>> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
>>> ---
>>>  arch/arm/kernel/topology.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
>>> index 71e1fec..6cc25a8 100644
>>> --- a/arch/arm/kernel/topology.c
>>> +++ b/arch/arm/kernel/topology.c
>>> @@ -42,7 +42,7 @@
>>>   */
>>>  static DEFINE_PER_CPU(unsigned long, cpu_scale);
>>>
>>> -unsigned long arch_scale_freq_power(struct sched_domain *sd, int cpu)
>>> +unsigned long arch_scale_cpu_power(struct sched_domain *sd, int cpu)
>>>  {
>>>       return per_cpu(cpu_scale, cpu);
>>>  }
>>> @@ -166,7 +166,7 @@ static void update_cpu_power(unsigned int cpu)
>>>       set_power_scale(cpu, cpu_capacity(cpu) / middle_capacity);
>>>
>>>       printk(KERN_INFO "CPU%u: update cpu_power %lu\n",
>>> -             cpu, arch_scale_freq_power(NULL, cpu));
>>> +             cpu, arch_scale_cpu_power(NULL, cpu));
>>>  }
>>>
>>>  #else
>>>
>>
> 

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