linux-kernel - Re: [PATCH v2] schedutil: Allow cpufreq requests to be made even when kthread kicked

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Date:   Tue, 22 May 2018 17:08:44 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     "Joel Fernandes (Google.)" <joelaf@...gle.com>,
        linux-kernel@...r.kernel.org,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Todd Kjos <tkjos@...gle.com>, claudio@...dence.eu.com,
        kernel-team@...roid.com, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2] schedutil: Allow cpufreq requests to be made even
 when kthread kicked

On 22-05-18, 13:31, Rafael J. Wysocki wrote:
> So below is my (compiled-only) version of the $subject patch, obviously based
> on the Joel's work.
> 
> Roughly, what it does is to move the fast_switch_enabled path entirely to
> sugov_update_single() and take the spinlock around sugov_update_commit()
> in the one-CPU case too.
> 
> ---
>  kernel/sched/cpufreq_schedutil.c |   57 ++++++++++++++++++++++++++-------------
>  1 file changed, 38 insertions(+), 19 deletions(-)
> 
> Index: linux-pm/kernel/sched/cpufreq_schedutil.c
> ===================================================================
> --- linux-pm.orig/kernel/sched/cpufreq_schedutil.c
> +++ linux-pm/kernel/sched/cpufreq_schedutil.c
> @@ -92,9 +92,6 @@ static bool sugov_should_update_freq(str
>  	    !cpufreq_can_do_remote_dvfs(sg_policy->policy))
>  		return false;
>  
> -	if (sg_policy->work_in_progress)
> -		return false;
> -
>  	if (unlikely(sg_policy->need_freq_update))
>  		return true;
>  
> @@ -103,25 +100,25 @@ static bool sugov_should_update_freq(str
>  	return delta_ns >= sg_policy->freq_update_delay_ns;
>  }
>  
> -static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
> -				unsigned int next_freq)
> +static bool sugov_update_next_freq(struct sugov_policy *sg_policy, u64 time,
> +				   unsigned int next_freq)
>  {
> -	struct cpufreq_policy *policy = sg_policy->policy;
> -
>  	if (sg_policy->next_freq == next_freq)
> -		return;
> +		return false;
>  
>  	sg_policy->next_freq = next_freq;
>  	sg_policy->last_freq_update_time = time;
>  
> -	if (policy->fast_switch_enabled) {
> -		next_freq = cpufreq_driver_fast_switch(policy, next_freq);
> -		if (!next_freq)
> -			return;
> +	return true;
> +}
>  
> -		policy->cur = next_freq;
> -		trace_cpu_frequency(next_freq, smp_processor_id());
> -	} else {
> +static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
> +				unsigned int next_freq)
> +{
> +	if (!sugov_update_next_freq(sg_policy, time, next_freq))
> +		return;
> +
> +	if (!sg_policy->work_in_progress) {
>  		sg_policy->work_in_progress = true;
>  		irq_work_queue(&sg_policy->irq_work);
>  	}
> @@ -277,6 +274,7 @@ static void sugov_update_single(struct u
>  {
>  	struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
>  	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> +	struct cpufreq_policy *policy = sg_policy->policy;
>  	unsigned long util, max;
>  	unsigned int next_f;
>  	bool busy;
> @@ -307,7 +305,23 @@ static void sugov_update_single(struct u
>  		sg_policy->cached_raw_freq = 0;
>  	}
>  
> -	sugov_update_commit(sg_policy, time, next_f);
> +	if (policy->fast_switch_enabled) {

Why do you assume that fast switch isn't possible in shared policy
cases ? It infact is already enabled for few drivers.

-- 
viresh