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 <[email protected]>
> ---
> 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().
Thanks,
Srinivas
