Re: [PATCH V2 0/3] Introduce Thermal Pressure

Thara Gopinath
2019-04-30T16:10:18Z

On 04/30/2019 10:39 AM, Ionela Voinescu wrote:
> Hi Thara,
>
> On 29/04/2019 14:29, Ionela Voinescu wrote:
>> Hi Thara,
>>
>>>
>>> Hackbench: (1 group , 30000 loops, 10 runs)
>>> Result Standard Deviation
>>> (Time Secs) (% of mean)
>>>
>>> No Thermal Pressure 10.21 7.99%
>>>
>>> Instantaneous thermal pressure 10.16 5.36%
>>>
>>> Thermal Pressure Averaging
>>> using PELT fmwk 9.88 3.94%
>>>
>>> Thermal Pressure Averaging
>>> non-PELT Algo. Decay : 500 ms 9.94 4.59%
>>>
>>> Thermal Pressure Averaging
>>> non-PELT Algo. Decay : 250 ms 7.52 5.42%
>>>
>>> Thermal Pressure Averaging
>>> non-PELT Algo. Decay : 125 ms 9.87 3.94%
>>>
>>>
>>
>> I'm trying your patches on my Hikey960 and I'm getting different results
>> than the ones here.
>>
>> I'm running with the step-wise governor, enabled only on the big cores.
>> The decay period is set to 250ms.
>>
>> The result for hackbench is:
>>
>> # ./hackbench -g 1 -l 30000
>> Running in process mode with 1 groups using 40 file descriptors each (== 40 tasks)
>> Each sender will pass 30000 messages of 100 bytes
>> Time: 20.756
>>
>> During the run I see the little cores running at maximum frequency
>> (1.84GHz) while the big cores run mostly at 1.8GHz, only sometimes capped
>> at 1.42GHz. There should not be any capacity inversion.
>> The temperature is kept around 75 degrees (73 to 77 degrees).
>>
>> I don't have any kind of active cooling (no fans on the board), only a
>> heatsink on the SoC.
>>
>> But as you see my results(~20s) are very far from the 7-10s in your
>> results.
>>
>> Do you see anything wrong with this process? Can you give me more
>> details on your setup that I can use to test on my board?
>>
>
> I've found that my poor results above were due to debug options
> mistakenly left enabled in the defconfig. Sorry about that!
>
> After cleaning it up I'm getting results around 5.6s for this test case.
> I've run 50 iterations for each test, with 90s cool down period between
> them.
>
>
> Hackbench: (1 group , 30000 loops, 50 runs)
> Result Standard Deviation
> (Time Secs) (% of mean)
>
> No Thermal Pressure(step_wise) 5.644 7.760%
> No Thermal Pressure(IPA) 5.677 9.062%
>
> Thermal Pressure Averaging
> non-PELT Algo. Decay : 250 ms 5.627 5.593%
> (step-wise, bigs capped only)
>
> Thermal Pressure Averaging
> non-PELT Algo. Decay : 250 ms 5.690 3.738%
> (IPA)
>
> All of the results above are within 1.1% difference with a
> significantly higher standard deviation.

Hi Ionela,

I have replied to your original emails without seeing this one. So,
interesting results. I see IPA is worse off (Slightly) than step wise in
both thermal pressure and non-thermal pressure scenarios. Did you try
500 ms decay period by any chance?

>
> I wanted to run this initially to validate my setup and understand
> if there is any conclusion we can draw from a test like this, that
> floods the CPUs with tasks. Looking over the traces, the tasks are
> running almost back to back, trying to use all available resources,
> on all the CPUs.
> Therefore, I doubt that there could be better decisions that could be
> made, knowing about thermal pressure, for this usecase.
>
> I'll try next some capacity inversion usecase and post the results when
> they are ready.

Sure. let me know if I can help.

Regards
Thara

>
> Hope it helps,
> Ionela.
>
>
>> Thank you,
>> Ionela.
>>

--
Regards
Thara