Re: [PATCH 4/5] intel_pstate: Remove C0 tracking

Yuyang Du
2014-05-09T09:49:30Z

Hi Dirk,

I don't get why you remove the c0 tracking. This is my understanding wrong.

Suppose it is removed, then the objective of the PID control is:

delta(aperf) / delta(mperf) * max_pstate / current_pstate

But delta(aperf) / delta(mperf) * max_pstate is the average frequency of the last
time frame, and current_pstate is the last requested frequency, then the
objective is:

last_freq_average / last_requested_freq ==> setpoint

What does it mean, SW satisfaction of freq request? Why control that?

Thanks
Yuyang

> @@ -561,46 +559,37 @@ static inline void intel_pstate_calc_busy(struct cpudata *cpu,
> struct sample *sample)
> {
> int32_t core_pct;
> - int32_t c0_pct;
>
> core_pct = div_fp(int_tofp((sample->aperf)),
> int_tofp((sample->mperf)));
> core_pct = mul_fp(core_pct, int_tofp(100));
> FP_ROUNDUP(core_pct);
>
> - c0_pct = div_fp(int_tofp(sample->mperf), int_tofp(sample->tsc));
> -
> sample->freq = fp_toint(
> mul_fp(int_tofp(cpu->pstate.max_pstate * 1000), core_pct));
>
> - sample->core_pct_busy = mul_fp(core_pct, c0_pct);
> + sample->core_pct_busy = core_pct;
> }