Re: [RFC] GPU-bound energy efficiency improvements for the intel_pstate driver (v2).

[Francisco Jerez <currojerez@riseup.net>]

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

> On Tue, 2020-03-10 at 14:41 -0700, Francisco Jerez wrote:
>> 
>
> [...]
>
>> Thanks in advance for any review feed-back and test reports.
>> 
>> [PATCH 01/10] PM: QoS: Add CPU_RESPONSE_FREQUENCY global PM QoS
>> limit.
>> [PATCH 02/10] drm/i915: Adjust PM QoS response frequency based on GPU
>> load.
>> [PATCH 03/10] OPTIONAL: drm/i915: Expose PM QoS control parameters
>> via debugfs.
>> [PATCH 04/10] Revert "cpufreq: intel_pstate: Drop ->update_util from
>> pstate_funcs"
>> [PATCH 05/10] cpufreq: intel_pstate: Implement VLP controller
>> statistics and status calculation.
>> [PATCH 06/10] cpufreq: intel_pstate: Implement VLP controller target
>> P-state range estimation.
>> [PATCH 07/10] cpufreq: intel_pstate: Implement VLP controller for HWP
>> parts.
>> [PATCH 08/10] cpufreq: intel_pstate: Enable VLP controller based on
>> ACPI FADT profile and CPUID.
>> [PATCH 09/10] OPTIONAL: cpufreq: intel_pstate: Add tracing of VLP
>> controller status.
>> [PATCH 10/10] OPTIONAL: cpufreq: intel_pstate: Expose VLP controller
>> parameters via debugfs.
>> 
> Do you have debug patch (You don't to submit as a patch), which will
> allow me to dynamically disable/enable all these changes? I want to
> compare and do some measurements.
>

Something like this (fully untested) patch?  It should prevent the VLP
controller from running if you do:

echo 16 > /sys/kernel/debug/pstate_snb/lp_debug

> Thanks,
> Srinivas 
>
>>[...]


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diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index ab893a211746..8749b4a14447 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2411,6 +2411,9 @@ static void intel_pstate_update_util(struct update_util_data *data, u64 time,
 static void intel_pstate_update_util_hwp_vlp(struct update_util_data *data,
 					     u64 time, unsigned int flags)
 {
+	if ((vlp_params.debug & 16))
+		return;
+
 	struct cpudata *cpu = container_of(data, struct cpudata, update_util);
 
 	if (update_vlp_sample(cpu, time, flags)) {

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