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

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Message-ID: <5CC87362.6080307@linaro.org>
Date:   Tue, 30 Apr 2019 12:10:10 -0400
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>, mingo@...hat.com,
        peterz@...radead.org, rui.zhang@...el.com
Cc:     linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        viresh.kumar@...aro.org, javi.merino@...nel.org,
        edubezval@...il.com, daniel.lezcano@...aro.org,
        vincent.guittot@...aro.org, nicolas.dechesne@...aro.org,
        bjorn.andersson@...aro.org, dietmar.eggemann@....com
Subject: Re: [PATCH V2 0/3] Introduce Thermal Pressure

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