Re: [PATCH V2 3/4] cpufreq: stats: Enable stats for fast-switch as well

From: Rafael J. Wysocki
Date: Wed Sep 23 2020 - 11:15:03 EST


On Wed, Sep 16, 2020 at 8:46 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
>
> Now that all the blockers are gone for enabling stats in fast-switching
> case, enable it.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> drivers/cpufreq/cpufreq.c | 6 +++++-
> drivers/cpufreq/cpufreq_stats.c | 6 ------
> 2 files changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 47aa90f9a7c2..d5fe64e96be9 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2057,8 +2057,12 @@ unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
> unsigned int target_freq)
> {
> target_freq = clamp_val(target_freq, policy->min, policy->max);
> + target_freq = cpufreq_driver->fast_switch(policy, target_freq);
>
> - return cpufreq_driver->fast_switch(policy, target_freq);
> + if (target_freq)
> + cpufreq_stats_record_transition(policy, target_freq);

So this adds two extra branches in the scheduler path for the cases
when the stats are not used at all which seems avoidable to some
extent.

Can we check policy->stats upfront here and bail out right away if it
is not set, for example?

> +
> + return target_freq;
> }
> EXPORT_SYMBOL_GPL(cpufreq_driver_fast_switch);
>
> diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
> index 314fa1d506d0..daea17f0c36c 100644
> --- a/drivers/cpufreq/cpufreq_stats.c
> +++ b/drivers/cpufreq/cpufreq_stats.c
> @@ -69,9 +69,6 @@ static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
> ssize_t len = 0;
> int i;
>
> - if (policy->fast_switch_enabled)
> - return 0;
> -
> for (i = 0; i < stats->state_num; i++) {
> if (pending) {
> if (i == stats->last_index)
> @@ -115,9 +112,6 @@ static ssize_t show_trans_table(struct cpufreq_policy *policy, char *buf)
> ssize_t len = 0;
> int i, j, count;
>
> - if (policy->fast_switch_enabled)
> - return 0;
> -
> len += scnprintf(buf + len, PAGE_SIZE - len, " From : To\n");
> len += scnprintf(buf + len, PAGE_SIZE - len, " : ");
> for (i = 0; i < stats->state_num; i++) {
> --
> 2.25.0.rc1.19.g042ed3e048af
>