linux-kernel - Re: [PATCH V2 1/2] sched: Factor out nr_iowait and nr_iowait

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Message-ID: <12842273.0tBlJJajS6@aspire.rjw.lan>
Date:   Fri, 26 Oct 2018 11:22:11 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     rafael@...nel.org, linux-pm@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "open list:SCHEDULER" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 1/2] sched: Factor out nr_iowait and nr_iowait_cpu

On Thursday, October 4, 2018 2:04:02 PM CEST Daniel Lezcano wrote:
> The function nr_iowait_cpu() can be used directly by nr_iowait() instead
> of duplicating code.
> 
> Call nr_iowait_cpu() from nr_iowait()
> 
> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  kernel/sched/core.c | 41 ++++++++++++++++++++---------------------
>  1 file changed, 20 insertions(+), 21 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 625bc98..43efb74 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2875,6 +2875,25 @@ unsigned long long nr_context_switches(void)
>  }
>  
>  /*
> + * Consumers of these two interfaces, like for example the cpufreq menu
> + * governor are using nonsensical data. Boosting frequency for a CPU that has
> + * IO-wait which might not even end up running the task when it does become
> + * runnable.
> + */
> +
> +unsigned long nr_iowait_cpu(int cpu)
> +{
> +	return atomic_read(&cpu_rq(cpu)->nr_iowait);
> +}
> +
> +void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
> +{
> +	struct rq *rq = this_rq();
> +	*nr_waiters = atomic_read(&rq->nr_iowait);
> +	*load = rq->load.weight;
> +}
> +
> +/*
>   * IO-wait accounting, and how its mostly bollocks (on SMP).
>   *
>   * The idea behind IO-wait account is to account the idle time that we could
> @@ -2909,31 +2928,11 @@ unsigned long nr_iowait(void)
>  	unsigned long i, sum = 0;
>  
>  	for_each_possible_cpu(i)
> -		sum += atomic_read(&cpu_rq(i)->nr_iowait);
> +		sum += nr_iowait_cpu(i);
>  
>  	return sum;
>  }
>  
> -/*
> - * Consumers of these two interfaces, like for example the cpufreq menu
> - * governor are using nonsensical data. Boosting frequency for a CPU that has
> - * IO-wait which might not even end up running the task when it does become
> - * runnable.
> - */
> -
> -unsigned long nr_iowait_cpu(int cpu)
> -{
> -	struct rq *this = cpu_rq(cpu);
> -	return atomic_read(&this->nr_iowait);
> -}
> -
> -void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
> -{
> -	struct rq *rq = this_rq();
> -	*nr_waiters = atomic_read(&rq->nr_iowait);
> -	*load = rq->load.weight;
> -}
> -
>  #ifdef CONFIG_SMP
>  
>  /*
> 

Both [1-2/2] applied with Peter's ACKs, thanks!