Hi Viresh,
I never use performance governor, but I want improved performance with ondemand.
Why do you suspect significant increased power? With ondemand the CPU will go down to lowest freq as soon as the load will decreased. And the measurement shows that the CPU load will decrease faster (because of faster calculation).
I build and distribute a 3.0.y kernel for a smart phone arm cortex A8. There are about 10000 installations with early_demand included. Nobody noticed increased power.
Though, I'm not able to provide numbers in the form of power.
Thanks,
Stratos
Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
>Hi Stratos,
>
>On 4 April 2013 05:00, Stratos Karafotis <stratosk@xxxxxxxxxxxx> wrote:
>> I tried to do some measurements simulating a CPU load with a loop that simply counts
>> an integer. The first test simulates a CPU load that lasts 2 x sampling_rate = ~ 20000us.
>> The second ~40000us and the third ~60000us.
>> There are 5 runs in each test. In each run the benchmark program counts 20 times with
>> early_demand off and 20 times with early_demand on and takes the average times.
>>
>> I run the benchmark program on 3.9-rc5 + early_demand patch. My CPU is the i7-3770 @ 3.40 GHz
>>
>> Please find below the results, and the benchmark code attached.
>> Please note, that the idea of this patch is to push the CPU to max frequency few sampling
>> periods (1 in most cases) earlier for a more responsive system.
>
>Yes, your results show some improvements. BUT if performance is the only thing
>we were looking for, then we will never use ondemand governor but performance
>governor.
>
>I suspect this little increase in performance must have increased power numbers
>too (significantly). So, if you can get numbers in the form of power/performance
>with and without your patch, it will be great.
>
>--
>viresh
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