[PlanetCCRMA] Performance degradation with kernel-rt-3.14.17-200.rt9.1.fc20.ccrma.x86_64

[Fernando Lopez-Lezcano]

On 09/09/2014 09:57 PM, Oleg Samarin wrote:
> I've made more testing
>
>>> echo "100" > /sys/devices/system/cpu/intel_pstate/min_perf_pct increases
>>> CPU does not speed up so much so it cann't be a workaround.
>>
>> How much faster does it go with min_perf_pct set to 100?
>
> Seems, it solves the issue:
>
> 3.4.17, min_perf_pct=100:
>          Core [core-id]  :Actual Freq (Mult.)	  C0%   Halt(C1)%  C3 %   C6 %
>          Core 1 [0]:	  4420.54 (44.21x)      26.8      56    8.22       1
>          Core 2 [1]:	  4483.19 (44.83x)      49.9     8.1    25.2       1
>          Core 3 [2]:	  4509.71 (45.10x)      9.28    21.2    65.5       1
>          Core 4 [3]:	  4559.41 (45.59x)      57.7    1.32    19.1    2.19

Glad to hear that!
That is my experience as well...

>>What do you see in the other variables in
>> /sys/devices/system/cpu/intel_pstate?
>
> There are only three variables:
>
> (3.4.17)
> max_perf_pct without=100
> min_perf_pct=33
> no_turbo=0

Another one to try is no_turbo - that would get you a more "even" speed 
but you loose speed when running processes on few cpus. It performed 
worse than no_turbo=0 in my limited tests.

-- Fernando