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

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Date:   Fri, 19 Jul 2019 03:42:58 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 18/24] PM / devfreq: tegra30: Optimize CPUFreq
 notifier

В Thu, 18 Jul 2019 18:48:42 +0900
Chanwoo Choi <cw00.choi@...sung.com> пишет:

> 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@...il.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.

I'd prefer to keep them separate for a sake of git bisection.

> > 
> > 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 
> 
>