Re: [Patch v6 0/7] Introduce Thermal Pressure

[Peter Zijlstra]

On Wed, Dec 11, 2019 at 11:11:41PM -0500, Thara Gopinath wrote:
> Test Results
> 
> Hackbench: 1 group , 30000 loops, 10 runs
>                                                Result         SD
>                                                (Secs)     (% of mean)
>  No Thermal Pressure                            14.03       2.69%
>  Thermal Pressure PELT Algo. Decay : 32 ms      13.29       0.56%
>  Thermal Pressure PELT Algo. Decay : 64 ms      12.57       1.56%
>  Thermal Pressure PELT Algo. Decay : 128 ms     12.71       1.04%
>  Thermal Pressure PELT Algo. Decay : 256 ms     12.29       1.42%
>  Thermal Pressure PELT Algo. Decay : 512 ms     12.42       1.15%
> 
> Dhrystone Run Time  : 20 threads, 3000 MLOOPS
>                                                  Result      SD
>                                                  (Secs)    (% of mean)
>  No Thermal Pressure                              9.452      4.49%
>  Thermal Pressure PELT Algo. Decay : 32 ms        8.793      5.30%
>  Thermal Pressure PELT Algo. Decay : 64 ms        8.981      5.29%
>  Thermal Pressure PELT Algo. Decay : 128 ms       8.647      6.62%
>  Thermal Pressure PELT Algo. Decay : 256 ms       8.774      6.45%
>  Thermal Pressure PELT Algo. Decay : 512 ms       8.603      5.41%

What is the conclusion, if any from these results? Clearly thermal
pressuse seems to help, but what window? ISTR we default to 32ms, which
is a wash for drystone, but sub-optimal for hackbench.


Anyway, the patches look more or less acceptible, just a bunch of nits,
the biggest being the fact that even if an architecture does not support
this there is still the code and runtime overhead.