Re: [PATCH v4 18/24] PM / devfreq: tegra30: Optimize CPUFreq notifier

Chanwoo Choi
2019-07-18T09:48:42Z

On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote:
> When CPU's memory activity is low or memory activity is high such that
> CPU's frequency contribution to the boosting is not taken into account,
> then there is no need to schedule devfreq's update. This eliminates
> unnecessary CPU activity during of idling caused by the scheduled work.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/devfreq/tegra30-devfreq.c | 73 +++++++++++++++++++++++++++----
> 1 file changed, 64 insertions(+), 9 deletions(-)

Patch4 add the 'cpufreq notifier' and this patch optimize the cpufreq notifier.
I think t hat you can combine two patches.

>
> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
> index 43c9c5fbfe91..8d6bf6e9f1ae 100644
> --- a/drivers/devfreq/tegra30-devfreq.c
> +++ b/drivers/devfreq/tegra30-devfreq.c
> @@ -216,10 +216,10 @@ static inline unsigned long do_percent(unsigned long val, unsigned int pct)
> return val * pct / 100;
> }
>
> -static unsigned long actmon_cpu_to_emc_rate(struct tegra_devfreq *tegra)
> +static unsigned long actmon_cpu_to_emc_rate(struct tegra_devfreq *tegra,
> + unsigned int cpu_freq)
> {
> const struct tegra_actmon_emc_ratio *ratio = actmon_emc_ratios;
> - unsigned int cpu_freq = cpufreq_get(0);
> unsigned int i;
>
> for (i = 0; i < ARRAY_SIZE(actmon_emc_ratios); i++, ratio++) {
> @@ -239,15 +239,15 @@ tegra_actmon_account_cpu_freq(struct tegra_devfreq *tegra,
> struct tegra_devfreq_device *dev,
> unsigned long target_freq)
> {
> - unsigned long static_cpu_emc_freq;
> + unsigned long cpu_emc_freq = 0;
>
> - if (dev->config->avg_dependency_threshold &&
> - dev->config->avg_dependency_threshold < dev->avg_freq) {
> - static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra);
> - target_freq = max(target_freq, static_cpu_emc_freq);
> - }
> + if (!dev->config->avg_dependency_threshold)
> + return target_freq;
>
> - return target_freq;
> + if (dev->avg_freq > dev->config->avg_dependency_threshold)
> + cpu_emc_freq = actmon_cpu_to_emc_rate(tegra, cpufreq_get(0));
> +
> + return max(target_freq, cpu_emc_freq);
> }
>
> static unsigned long tegra_actmon_lower_freq(struct tegra_devfreq *tegra,
> @@ -531,16 +531,71 @@ static void tegra_actmon_delayed_update(struct work_struct *work)
> mutex_unlock(&tegra->devfreq->lock);
> }
>
> +static unsigned long
> +tegra_actmon_cpufreq_contribution(struct tegra_devfreq *tegra,
> + unsigned int cpu_freq)
> +{
> + unsigned long freq, static_cpu_emc_freq;
> +
> + /* check whether CPU's freq is taken into account at all */
> + if (tegra->devices[MCCPU].avg_freq <=
> + tegra->devices[MCCPU].config->avg_dependency_threshold)
> + return 0;
> +
> + static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra, cpu_freq);
> +
> + /* compare static CPU-EMC freq with MCALL */
> + freq = tegra->devices[MCALL].avg_freq +
> + tegra->devices[MCALL].boost_freq;
> +
> + freq = tegra_actmon_upper_freq(tegra, freq);
> +
> + if (freq == tegra->max_freq || freq >= static_cpu_emc_freq)
> + return 0;
> +
> + /* compare static CPU-EMC freq with MCCPU */
> + freq = tegra->devices[MCCPU].avg_freq +
> + tegra->devices[MCCPU].boost_freq;
> +
> + freq = tegra_actmon_upper_freq(tegra, freq);
> +
> + if (freq == tegra->max_freq || freq >= static_cpu_emc_freq)
> + return 0;
> +
> + return static_cpu_emc_freq;
> +}
> +
> static int tegra_actmon_cpu_notify_cb(struct notifier_block *nb,
> unsigned long action, void *ptr)
> {
> + struct cpufreq_freqs *freqs = ptr;
> struct tegra_devfreq *tegra;
> + unsigned long old, new;
>
> if (action != CPUFREQ_POSTCHANGE)
> return NOTIFY_OK;
>
> tegra = container_of(nb, struct tegra_devfreq, cpu_rate_change_nb);
>
> + /*
> + * Quickly check whether CPU frequency should be taken into account
> + * at all, without blocking CPUFreq's core.
> + */
> + if (mutex_trylock(&tegra->devfreq->lock)) {
> + old = tegra_actmon_cpufreq_contribution(tegra, freqs->old);
> + new = tegra_actmon_cpufreq_contribution(tegra, freqs->new);
> + mutex_unlock(&tegra->devfreq->lock);
> +
> + /*
> + * If CPU's frequency shouldn't be taken into account at
> + * the moment, then there is no need to update the devfreq's
> + * state because ISR will re-check CPU's frequency on the
> + * next interrupt.
> + */
> + if (old == new)
> + return NOTIFY_OK;
> + }
> +
> /*
> * CPUFreq driver should support CPUFREQ_ASYNC_NOTIFICATION in order
> * to allow asynchronous notifications. This means we can't block
>

--
Best Regards,
Chanwoo Choi
Samsung Electronics