Intel_pstate: One Core always 100% C0 state and never scale down

[Light]

I am using a laptop with Intel Ivy bridge core i7 3610QM. I updated my
kernel to 3.10 and started to use intel_pstate as scaling driver:
#cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
intel_pstate

However I find that one of my four cores is always in C0 state even when
there is no activities. I monitored it using i7z:
Core [core-id] :Actual Freq (Mult.) C0% Halt(C1)% C3 % C6 %
C7 % Temp
Core 1 [0]: 3288.24 (32.97x) 99.7 0 0
0 0 83
Core 2 [1]: 3138.62 (31.47x) 1 0 0
0 99.7 74
Core 3 [2]: 3175.46 (31.84x) 1 0.891 0
0 99 76
Core 4 [3]: 3177.34 (31.86x) 1 0.21 0
0 99.3 71

Also cpu frequencies never scale down, resulting in very high temp.
#cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
powersave

It does say powersave, and my cpu is capable of 1.20Ghz to 3.30Ghz

I don't know if I misconfigured or misunderstood something. Can someone
tell me why?
Thanks!
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[Light]

On 07/04/2013 11:43 AM, Light wrote:
> I am using a laptop with Intel Ivy bridge core i7 3610QM. I updated my
> kernel to 3.10 and started to use intel_pstate as scaling driver:
> #cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
> intel_pstate
>
> However I find that one of my four cores is always in C0 state even
> when there is no activities. I monitored it using i7z:
> Core [core-id] :Actual Freq (Mult.) C0% Halt(C1)% C3 % C6 %
> C7 % Temp
> Core 1 [0]: 3288.24 (32.97x) 99.7 0 0
> 0 0 83
> Core 2 [1]: 3138.62 (31.47x) 1 0 0
> 0 99.7 74
> Core 3 [2]: 3175.46 (31.84x) 1 0.891 0
> 0 99 76
> Core 4 [3]: 3177.34 (31.86x) 1 0.21 0
> 0 99.3 71
>
> Also cpu frequencies never scale down, resulting in very high temp.
> #cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> powersave
>
> It does say powersave, and my cpu is capable of 1.20Ghz to 3.30Ghz
>
> I don't know if I misconfigured or misunderstood something. Can
> someone tell me why?
> Thanks!

Switching to dynticks Idle fixed the problem. But I am still wondering
if it were a bug with full dynticks...