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SubjectRe: [Resend][PATCH V2] cpufreq: intel_pstate: allow trace in passive mode
On Tue, Dec 19, 2017 at 12:30 AM, Srinivas Pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
> On Fri, 2017-12-15 at 16:43 -0800, Doug Smythies wrote:
>> Allow use of the trace_pstate_sample trace function
>> when the intel_pstate driver is in passive mode.
>> Since the core_busy and scaled_busy fields are not
>> used, and it might be desirable to know which path
>> through the driver was used, either intel_cpufreq_target
>> or intel_cpufreq_fast_switch, re-task the core_busy
>> field as a flag indicator.
>>
>> The user can then use the intel_pstate_tracer.py utility
>> to summarize and plot the trace.
>>
>> In Passive mode the driver is only called if there is
>> a need to change the target frequency, so durations
>> (time gaps between calls) can be very very long. The user
>> needs to understand, and not be confused by, this limitation.
>>
>> V2: prepare for resend. Rebase to current kernel, 4.15-rc3.
>> Signed-off-by: Doug Smythies <dsmythies@telus.net>
>> ---
>> drivers/cpufreq/intel_pstate.c | 50
>> ++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 48 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/cpufreq/intel_pstate.c
>> b/drivers/cpufreq/intel_pstate.c
>> index 93a0e88..fe25d69 100644
>> --- a/drivers/cpufreq/intel_pstate.c
>> +++ b/drivers/cpufreq/intel_pstate.c
>> @@ -1949,7 +1949,10 @@ static int intel_cpufreq_target(struct
>> cpufreq_policy *policy,
>> {
>> struct cpudata *cpu = all_cpu_data[policy->cpu];
>> struct cpufreq_freqs freqs;
>> - int target_pstate;
>> + struct sample *sample;
>> + int target_pstate, from;
>> + u64 time;
>> + bool sample_taken;
>>
>> update_turbo_state();
>>
>> @@ -1969,12 +1972,32 @@ static int intel_cpufreq_target(struct
>> cpufreq_policy *policy,
>> break;
>> }
>> target_pstate = intel_pstate_prepare_request(cpu,
>> target_pstate);
>> +
>> + from = cpu->pstate.current_pstate;
>> + time = ktime_get();
>> + sample_taken = intel_pstate_sample(cpu, time);
>> +
> This is quite a bit of overhead for tracing. Why not fold the above two
> statements in the next if () with conditional tracing?
>
>> if (target_pstate != cpu->pstate.current_pstate) {
>> cpu->pstate.current_pstate = target_pstate;
>> wrmsrl_on_cpu(policy->cpu, MSR_IA32_PERF_CTL,
>> pstate_funcs.get_val(cpu,
>> target_pstate));
>> }
>> freqs.new = target_pstate * cpu->pstate.scaling;
>> +
>> + if (sample_taken) {
> if (trace_pstate_sample_enabled() && sample_taken) {
>
>> + intel_pstate_calc_avg_perf(cpu);
>> + sample = &cpu->sample;
>> + trace_pstate_sample(0,
> Not sure they are statement below are aligned correctly.
>
>> + 0,
>> + from,
>> + cpu->pstate.current_pstate,
>> + sample->mperf,
>> + sample->aperf,
>> + sample->tsc,
>> + get_avg_frequency(cpu),
>> + fp_toint(cpu->iowait_boost * 100));
>> + }
>> +
> Same below in the intel_cpufreq_fast_switch().

And it's quite a bit of code duplication too.

Maybe put this into a separate function and call it from the two places?

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