Re: [PATCH 07/10] cpufreq: intel_pstate: Implement VLP controller for HWP parts.

[Francisco Jerez <currojerez@riseup.net>]

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"Pandruvada, Srinivas" <srinivas.pandruvada@intel.com> writes:

> On Tue, 2020-03-10 at 14:42 -0700, Francisco Jerez wrote:
>> This implements a simple variably low-pass-filtering governor in
>> control of the HWP MIN/MAX PERF range based on the previously
>> introduced get_vlp_target_range().  See "cpufreq: intel_pstate:
>> Implement VLP controller target P-state range estimation." for the
>> rationale.
>
> I just gave a try on a pretty idle system with just systemd processes
> and usual background tasks with nomodset. 
>
> I see that there HWP min is getting changed between 4-8. Why are
> changing HWP dynamic range even on an idle system running no where
> close to TDP?
>

The HWP request range is clamped to the frequency range specified by the
CPUFREQ policy and to the cpu->pstate.min_pstate bound.

If you see the HWP minimum fluctuating above that it's likely a sign of
your system not being completely idle -- If that's the case it's likely
to go away after you do:

 echo 0 > /sys/kernel/debug/pstate_snb/vlp_realtime_gain_pml

> Thanks,
> Srinivas
>
>
>> 
>> Signed-off-by: Francisco Jerez <currojerez@riseup.net>
>> ---
>>  drivers/cpufreq/intel_pstate.c | 79
>> +++++++++++++++++++++++++++++++++-
>>  1 file changed, 77 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/cpufreq/intel_pstate.c
>> b/drivers/cpufreq/intel_pstate.c
>> index cecadfec8bc1..a01eed40d897 100644
>> --- a/drivers/cpufreq/intel_pstate.c
>> +++ b/drivers/cpufreq/intel_pstate.c
>> @@ -1905,6 +1905,20 @@ static void intel_pstate_reset_vlp(struct
>> cpudata *cpu)
>>  	vlp->gain = max(1, div_fp(1000, vlp_params.setpoint_0_pml));
>>  	vlp->target.p_base = 0;
>>  	vlp->stats.last_response_frequency_hz = vlp_params.avg_hz;
>> +
>> +	if (hwp_active) {
>> +		const uint32_t p0 = max(cpu->pstate.min_pstate,
>> +					cpu->min_perf_ratio);
>> +		const uint32_t p1 = max_t(uint32_t, p0, cpu-
>> >max_perf_ratio);
>> +		const uint64_t hwp_req = (READ_ONCE(cpu-
>> >hwp_req_cached) &
>> +					  ~(HWP_MAX_PERF(~0L) |
>> +					    HWP_MIN_PERF(~0L) |
>> +					    HWP_DESIRED_PERF(~0L))) |
>> +					 HWP_MIN_PERF(p0) |
>> HWP_MAX_PERF(p1);
>> +
>> +		wrmsrl_on_cpu(cpu->cpu, MSR_HWP_REQUEST, hwp_req);
>> +		cpu->hwp_req_cached = hwp_req;
>> +	}
>>  }
>>  
>>  /**
>> @@ -2222,6 +2236,46 @@ static void intel_pstate_adjust_pstate(struct
>> cpudata *cpu)
>>  		fp_toint(cpu->iowait_boost * 100));
>>  }
>>  
>> +static void intel_pstate_adjust_pstate_range(struct cpudata *cpu,
>> +					     const unsigned int
>> range[])
>> +{
>> +	const int from = cpu->hwp_req_cached;
>> +	unsigned int p0, p1, p_min, p_max;
>> +	struct sample *sample;
>> +	uint64_t hwp_req;
>> +
>> +	update_turbo_state();
>> +
>> +	p0 = max(cpu->pstate.min_pstate, cpu->min_perf_ratio);
>> +	p1 = max_t(unsigned int, p0, cpu->max_perf_ratio);
>> +	p_min = clamp_t(unsigned int, range[0], p0, p1);
>> +	p_max = clamp_t(unsigned int, range[1], p0, p1);
>> +
>> +	trace_cpu_frequency(p_max * cpu->pstate.scaling, cpu->cpu);
>> +
>> +	hwp_req = (READ_ONCE(cpu->hwp_req_cached) &
>> +		   ~(HWP_MAX_PERF(~0L) | HWP_MIN_PERF(~0L) |
>> +		     HWP_DESIRED_PERF(~0L))) |
>> +		  HWP_MIN_PERF(vlp_params.debug & 2 ? p0 : p_min) |
>> +		  HWP_MAX_PERF(vlp_params.debug & 4 ? p1 : p_max);
>> +
>> +	if (hwp_req != cpu->hwp_req_cached) {
>> +		wrmsrl(MSR_HWP_REQUEST, hwp_req);
>> +		cpu->hwp_req_cached = hwp_req;
>> +	}
>> +
>> +	sample = &cpu->sample;
>> +	trace_pstate_sample(mul_ext_fp(100, sample->core_avg_perf),
>> +			    fp_toint(sample->busy_scaled),
>> +			    from,
>> +			    hwp_req,
>> +			    sample->mperf,
>> +			    sample->aperf,
>> +			    sample->tsc,
>> +			    get_avg_frequency(cpu),
>> +			    fp_toint(cpu->iowait_boost * 100));
>> +}
>> +
>>  static void intel_pstate_update_util(struct update_util_data *data,
>> u64 time,
>>  				     unsigned int flags)
>>  {
>> @@ -2260,6 +2314,22 @@ static void intel_pstate_update_util(struct
>> update_util_data *data, u64 time,
>>  		intel_pstate_adjust_pstate(cpu);
>>  }
>>  
>> +/**
>> + * Implementation of the cpufreq update_util hook based on the VLP
>> + * controller (see get_vlp_target_range()).
>> + */
>> +static void intel_pstate_update_util_hwp_vlp(struct update_util_data
>> *data,
>> +					     u64 time, unsigned int
>> flags)
>> +{
>> +	struct cpudata *cpu = container_of(data, struct cpudata,
>> update_util);
>> +
>> +	if (update_vlp_sample(cpu, time, flags)) {
>> +		const struct vlp_target_range *target =
>> +			get_vlp_target_range(cpu);
>> +		intel_pstate_adjust_pstate_range(cpu, target->value);
>> +	}
>> +}
>> +
>>  static struct pstate_funcs core_funcs = {
>>  	.get_max = core_get_max_pstate,
>>  	.get_max_physical = core_get_max_pstate_physical,
>> @@ -2389,6 +2459,9 @@ static int intel_pstate_init_cpu(unsigned int
>> cpunum)
>>  
>>  	intel_pstate_get_cpu_pstates(cpu);
>>  
>> +	if (pstate_funcs.update_util ==
>> intel_pstate_update_util_hwp_vlp)
>> +		intel_pstate_reset_vlp(cpu);
>> +
>>  	pr_debug("controlling: cpu %d\n", cpunum);
>>  
>>  	return 0;
>> @@ -2398,7 +2471,8 @@ static void
>> intel_pstate_set_update_util_hook(unsigned int cpu_num)
>>  {
>>  	struct cpudata *cpu = all_cpu_data[cpu_num];
>>  
>> -	if (hwp_active && !hwp_boost)
>> +	if (hwp_active && !hwp_boost &&
>> +	    pstate_funcs.update_util !=
>> intel_pstate_update_util_hwp_vlp)
>>  		return;
>>  
>>  	if (cpu->update_util_set)
>> @@ -2526,7 +2600,8 @@ static int intel_pstate_set_policy(struct
>> cpufreq_policy *policy)
>>  		 * was turned off, in that case we need to clear the
>>  		 * update util hook.
>>  		 */
>> -		if (!hwp_boost)
>> +		if (!hwp_boost && pstate_funcs.update_util !=
>> +				  intel_pstate_update_util_hwp_vlp)
>>  			intel_pstate_clear_update_util_hook(policy-
>> >cpu);
>>  		intel_pstate_hwp_set(policy->cpu);
>>  	}

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