linux-kernel - Re: [Patch v6 2/7] sched: Add hook to read per cpu thermal pressure.

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Message-ID: <20191216143539.GR2844@hirez.programming.kicks-ass.net>
Date:   Mon, 16 Dec 2019 15:35:39 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     mingo@...hat.com, ionela.voinescu@....com,
        vincent.guittot@...aro.org, rui.zhang@...el.com,
        qperret@...gle.com, daniel.lezcano@...aro.org,
        viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
        amit.kachhap@...il.com, javi.merino@...nel.org,
        amit.kucheria@...durent.com
Subject: Re: [Patch v6 2/7] sched: Add hook to read per cpu thermal pressure.

On Wed, Dec 11, 2019 at 11:11:43PM -0500, Thara Gopinath wrote:
> Introduce arch_scale_thermal_capacity to retrieve per cpu thermal
> pressure.
> 
> Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
> ---
>  include/linux/sched/topology.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index f341163..f1e22f9 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -225,6 +225,14 @@ unsigned long arch_scale_cpu_capacity(int cpu)
>  }
>  #endif
>  
> +#ifndef arch_scale_thermal_capacity
> +static __always_inline
> +unsigned long arch_scale_thermal_capacity(int cpu)
> +{
> +	return 0;
> +}
> +#endif

This is confusing, the return value is not a capacity, it is a reduction
in capacity. Either a comment of a better name would be appreciated.