Disabling power management firmware decisions

Disabling power management firmware decisions

[Daniel Lezcano]

Hi,

I would like to do some experiments with the x86 platform but I am 
facing one big issue.

When I use the rapl register to measure the energy consumption with 
turbostat and another tool written by me. I see no differences between 
my kernel changes while using the idlestat tool, I see big differences 
in the idle state durations with the traces.

I remember on x86 the firmware overrides all kernel decisions to do the 
power management. So I assume, it is possible my changes are not 
measurable because of that.

Is there a way to tell the firmware to stop overriding the kernel 
decisions in order to let the kernel handle idle/dvfs on its own ?

Thanks

   -- Daniel


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Re: Disabling power management firmware decisions

[Rafael J. Wysocki]

On Thursday, March 19, 2015 02:33:34 PM Daniel Lezcano wrote:
> 
> Hi,
> 
> I would like to do some experiments with the x86 platform but I am 
> facing one big issue.
> 
> When I use the rapl register to measure the energy consumption with 
> turbostat and another tool written by me. I see no differences between 
> my kernel changes while using the idlestat tool, I see big differences 
> in the idle state durations with the traces.
> 
> I remember on x86 the firmware overrides all kernel decisions to do the 
> power management. So I assume, it is possible my changes are not 
> measurable because of that.
> 
> Is there a way to tell the firmware to stop overriding the kernel 
> decisions in order to let the kernel handle idle/dvfs on its own ?

The short answer to that is no, there isn't.  It also may not be firmware,
but hardware.

Rafael

Re: Disabling power management firmware decisions

[Daniel Lezcano]

On 03/19/2015 03:08 PM, Rafael J. Wysocki wrote:
> On Thursday, March 19, 2015 02:33:34 PM Daniel Lezcano wrote:
>>
>> Hi,
>>
>> I would like to do some experiments with the x86 platform but I am
>> facing one big issue.
>>
>> When I use the rapl register to measure the energy consumption with
>> turbostat and another tool written by me. I see no differences between
>> my kernel changes while using the idlestat tool, I see big differences
>> in the idle state durations with the traces.
>>
>> I remember on x86 the firmware overrides all kernel decisions to do the
>> power management. So I assume, it is possible my changes are not
>> measurable because of that.
>>
>> Is there a way to tell the firmware to stop overriding the kernel
>> decisions in order to let the kernel handle idle/dvfs on its own ?
>
> The short answer to that is no, there isn't.  It also may not be firmware,
> but hardware.

mmrfh, that's not funny :(

Thanks for the answer.

   -- Daniel

-- 
  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

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