linux-kernel - Re: [PATCH V4 2/3] sched/core: Rename schedutil_cpu_util() and allow rest of the kernel to use it

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Date:   Tue, 24 Nov 2020 09:10:19 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-kernel@...r.kernel.org, Lukasz Luba <lukasz.luba@....com>,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH V4 2/3] sched/core: Rename schedutil_cpu_util() and allow
 rest of the kernel to use it

Hey Viresh,

On Tuesday 24 Nov 2020 at 11:56:15 (+0530), Viresh Kumar wrote:
> There is nothing schedutil specific in schedutil_cpu_util(), rename it
> to effective_cpu_util(). Also create and expose another wrapper
> sched_cpu_util() which can be used by other parts of the kernel, like
> thermal core (that will be done in a later commit).
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  include/linux/sched.h            | 21 +++++++++++++++++++++
>  kernel/sched/core.c              | 11 +++++++++--
>  kernel/sched/cpufreq_schedutil.c |  2 +-
>  kernel/sched/fair.c              |  6 +++---
>  kernel/sched/sched.h             | 19 ++-----------------
>  5 files changed, 36 insertions(+), 23 deletions(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 063cd120b459..926b944dae5e 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1926,6 +1926,27 @@ extern long sched_getaffinity(pid_t pid, struct cpumask *mask);
>  #define TASK_SIZE_OF(tsk)	TASK_SIZE
>  #endif
>  
> +#ifdef CONFIG_SMP
> +/**
> + * enum cpu_util_type - CPU utilization type
> + * @FREQUENCY_UTIL:	Utilization used to select frequency
> + * @ENERGY_UTIL:	Utilization used during energy calculation
> + *
> + * The utilization signals of all scheduling classes (CFS/RT/DL) and IRQ time
> + * need to be aggregated differently depending on the usage made of them. This
> + * enum is used within sched_cpu_util() to differentiate the types of
> + * utilization expected by the callers, and adjust the aggregation accordingly.
> + */
> +enum cpu_util_type {
> +	FREQUENCY_UTIL,
> +	ENERGY_UTIL,
> +};
> +
> +/* Returns effective CPU utilization, as seen by the scheduler */
> +unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
> +			     unsigned long max);

Are 'type' and 'max' useful to anybody outside of kernel/sched ?
If not then how about we hide them, keep the cpu_util_type enum in
kernel/sched/sched.h and evaluate arch_scale_cpu_capacity() in
sched_cpu_util() directly?

Thanks,
Quentin