Re: [RFC PATCH 3/4] cpufreq: Add Active Stats calls tracking frequency changes

[Lukasz Luba]

On 6/22/21 10:32 AM, Viresh Kumar wrote:
> Not commenting on the idea itself but just the code changes here.
>
> On 22-06-21, 08:59, Lukasz Luba wrote:
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 802abc925b2a..d79cb9310572 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -14,6 +14,7 @@
> >   
> >   #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> >   
> > +#include <linux/active_stats.h>
> >   #include <linux/cpu.h>
> >   #include <linux/cpufreq.h>
> >   #include <linux/cpu_cooling.h>
> > @@ -387,6 +388,8 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy,
> >   
> >   		cpufreq_stats_record_transition(policy, freqs->new);
> >   		policy->cur = freqs->new;
> > +
> > +		active_stats_cpu_freq_change(policy->cpu, freqs->new);
> >   	}
> >   }
> >   
> > @@ -2085,6 +2088,8 @@ unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
> >   			    policy->cpuinfo.max_freq);
> >   	cpufreq_stats_record_transition(policy, freq);
> >   
> > +	active_stats_cpu_freq_fast_change(policy->cpu, freq);
> > +
>
> It would have been better if you would have modified
> cpufreq_stats_record_transition() instead, since that is there for
> similar kind of stats.

That cpufreq_stats_record_transition() is present only if
CONFIG_CPU_FREQ_STAT is set. I didn't wanted to be dependent on
this config.

> Plus don't you need to record this for all policy->cpus instead of
> just policy->cpu ?

It will be accounted for all cpus in that freq domain. The
active_stats_cpu_freq_fast_change() implementation uses
a shared structure (single for whole domain) 'shared_ast':
_active_stats_cpu_freq_change(ast->shared_ast, freq, ts)
(from patch 1/4)