linux-kernel - Re: [PATCH] sched/cpufreq: Align trace event behavior of fast switching

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Message-ID: <3316959.EEulJYEQYJ@kreacher>
Date:   Mon, 26 Aug 2019 11:10:52 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Douglas RAILLARD <douglas.raillard@....com>, peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        viresh.kumar@...aro.org, mingo@...hat.com
Subject: Re: [PATCH] sched/cpufreq: Align trace event behavior of fast switching

On Wednesday, August 7, 2019 5:33:40 PM CEST Douglas RAILLARD wrote:
> Fast switching path only emits an event for the CPU of interest, whereas the
> regular path emits an event for all the CPUs that had their frequency changed,
> i.e. all the CPUs sharing the same policy.
> 
> With the current behavior, looking at cpu_frequency event for a given CPU that
> is using the fast switching path will not give the correct frequency signal.
> 
> Signed-off-by: Douglas RAILLARD <douglas.raillard@....com>
> ---
>  kernel/sched/cpufreq_schedutil.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 1f82ab108bab..975ccc3de807 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -153,6 +153,7 @@ static void sugov_fast_switch(struct sugov_policy *sg_policy, u64 time,
>  			      unsigned int next_freq)
>  {
>  	struct cpufreq_policy *policy = sg_policy->policy;
> +	int cpu;
>  
>  	if (!sugov_update_next_freq(sg_policy, time, next_freq))
>  		return;
> @@ -162,7 +163,11 @@ static void sugov_fast_switch(struct sugov_policy *sg_policy, u64 time,
>  		return;
>  
>  	policy->cur = next_freq;
> -	trace_cpu_frequency(next_freq, smp_processor_id());
> +
> +	if (trace_cpu_frequency_enabled()) {
> +		for_each_cpu(cpu, policy->cpus)
> +			trace_cpu_frequency(next_freq, cpu);
> +	}
>  }
>  
>  static void sugov_deferred_update(struct sugov_policy *sg_policy, u64 time,
> 

Peter, any comments here?