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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc:     Doug Smythies <doug.smythies@gmail.com>, dsmythies@telus.net,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH V5] cpufreq: intel_pstate: allow trace in passive mode
Date:   Tue, 15 May 2018 11:05:11 +0200
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On Monday, May 14, 2018 5:35:41 PM CEST Srinivas Pandruvada wrote:
> On Sun, 2018-05-13 at 10:43 +0200, Rafael J. Wysocki wrote:
> > On Thursday, May 3, 2018 8:22:47 AM CEST 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.
> > > 
> > > Note: The core_busy feild still goes by that name
> > > in include/trace/events/power.h and within the
> > > intel_pstate_tracer.py script and csv file headers,
> > > but it is graphed as "performance", and called
> > > core_avg_perf now in the intel_pstate driver.
> > > 
> > > Sometimes, in passive mode, the driver is not called for
> > > many tens or even hundreds of seconds. The user
> > > needs to understand, and not be confused by, this limitation.
> > > 
> > > Signed-off-by: Doug Smythies <dsmythies@telus.net>
> > 
> > Srinivas, any comments or concerns?
> > 
> Looks fine. But as rest of code, prefer a newline after return.
> So I am sending V6 version only with that change.
> 
> Thanks,
> Srinivas
> > > 
> > > ---
> > > 
> > > V5: Changes as per Rafael J. Wysocki feedback.
> > >     See: https://lkml.org/lkml/2018/1/7/270
> > > 
> > > V4: Only execute the trace specific overhead code if trace
> > >     is enabled. Suggested by Srinivas Pandruvada.
> > > 
> > > V3: Move largely duplicate code to a subroutine.
> > >     Suggested by Rafael J. Wysocki.
> > > 
> > > V2: prepare for resend. Rebase to current kernel, 4.15-rc3.
> > > 
> > > ---
> > >  drivers/cpufreq/intel_pstate.c | 44
> > > ++++++++++++++++++++++++++++++++++++++++--
> > >  1 file changed, 42 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/cpufreq/intel_pstate.c
> > > b/drivers/cpufreq/intel_pstate.c
> > > index 17e566af..4a08686 100644
> > > --- a/drivers/cpufreq/intel_pstate.c
> > > +++ b/drivers/cpufreq/intel_pstate.c
> > > @@ -1939,13 +1939,49 @@ static int
> > > intel_cpufreq_verify_policy(struct cpufreq_policy *policy)
> > >  	return 0;
> > >  }
> > >  
> > > +/* Use of trace in passive mode:
> > > + *
> > > + * In passive mode the trace core_busy field (also known as the
> > > + * performance field, and lablelled as such on the graphs; also
> > > known as
> > > + * core_avg_perf) is not needed and so is re-assigned to indicate
> > > if the
> > > + * driver call was via the normal or fast switch path. Various
> > > graphs
> > > + * output from the intel_pstate_tracer.py utility that include
> > > core_busy
> > > + * (or performance or core_avg_perf) have a fixed y-axis from 0 to
> > > 100%,
> > > + * so we use 10 to indicate the the normal path through the
> > > driver, and
> > > + * 90 to indicate the fast switch path through the driver.
> > > + * The scaled_busy field is not used, and is set to 0.
> > > + */
> > > +
> > > +#define	INTEL_PSTATE_TRACE_TARGET 10
> > > +#define	INTEL_PSTATE_TRACE_FAST_SWITCH 90
> > > +
> > > +static void intel_cpufreq_trace(struct cpudata *cpu, unsigned int
> > > trace_type, int old_pstate)
> > > +{
> > > +	struct sample *sample;
> > > +
> > > +	if (!trace_pstate_sample_enabled())
> > > +		return;
> one newline
> 
> > > +	if (!intel_pstate_sample(cpu, ktime_get()))
> > > +		return;
> one new line
> 
> > > +	sample = &cpu->sample;
> > > +	trace_pstate_sample(trace_type,
> > > +		0,
> > > +		old_pstate,
> > > +		cpu->pstate.current_pstate,
> > > +		sample->mperf,
> > > +		sample->aperf,
> > > +		sample->tsc,
> > > +		get_avg_frequency(cpu),
> > > +		fp_toint(cpu->iowait_boost * 100));
> > > +}
> > > +
> > >  static int intel_cpufreq_target(struct cpufreq_policy *policy,
> > >  				unsigned int target_freq,
> > >  				unsigned int relation)
> > >  {
> > >  	struct cpudata *cpu = all_cpu_data[policy->cpu];
> > >  	struct cpufreq_freqs freqs;
> > > -	int target_pstate;
> > > +	int target_pstate, old_pstate;
> > >  
> > >  	update_turbo_state();
> > >  
> > > @@ -1965,12 +2001,14 @@ static int intel_cpufreq_target(struct
> > > cpufreq_policy *policy,
> > >  		break;
> > >  	}
> > >  	target_pstate = intel_pstate_prepare_request(cpu,
> > > target_pstate);
> > > +	old_pstate = cpu->pstate.current_pstate;
> > >  	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;
> > > +	intel_cpufreq_trace(cpu, INTEL_PSTATE_TRACE_TARGET,
> > > old_pstate);
> > >  	cpufreq_freq_transition_end(policy, &freqs, false);
> > >  
> > >  	return 0;
> > > @@ -1980,13 +2018,15 @@ static unsigned int
> > > intel_cpufreq_fast_switch(struct cpufreq_policy *policy,
> > >  					      unsigned int
> > > target_freq)
> > >  {
> > >  	struct cpudata *cpu = all_cpu_data[policy->cpu];
> > > -	int target_pstate;
> > > +	int target_pstate, old_pstate;
> > >  
> > >  	update_turbo_state();
> > >  
> > >  	target_pstate = DIV_ROUND_UP(target_freq, cpu-
> > > >pstate.scaling);
> > >  	target_pstate = intel_pstate_prepare_request(cpu,
> > > target_pstate);
> > > +	old_pstate = cpu->pstate.current_pstate;
> > >  	intel_pstate_update_pstate(cpu, target_pstate);
> > > +	intel_cpufreq_trace(cpu, INTEL_PSTATE_TRACE_FAST_SWITCH,
> > > old_pstate);
> > >  	return target_pstate * cpu->pstate.scaling;
> > >  }
> > >  
> > > 
> > 
> > 
> 

Applied, thanks!