linux-kernel - Re: [PATCH] PM:EM: fix wrong utilization estimation in em_cpu

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Date: Thu, 4 Apr 2024 12:05:41 +0100
From: Lukasz Luba <lukasz.luba@....com>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: rui.zhang@...el.com, amit.kucheria@...durent.com, amit.kachhap@...il.com,
 daniel.lezcano@...aro.org, viresh.kumar@...aro.org, len.brown@...el.com,
 pavel@....cz, mhiramat@...nel.org, qyousef@...alina.io, wvw@...gle.com,
 xuewen.yan94@...il.com, rafael@...nel.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org, dietmar.eggemann@....com
Subject: Re: [PATCH] PM:EM: fix wrong utilization estimation in
 em_cpu_energy()

Hi Vincent,

On 4/4/24 11:42, Vincent Guittot wrote:
> Commit 1b600da51073 ("PM: EM: Optimize em_cpu_energy() and remove division")
> has added back map_util_perf() in em_cpu_energy() computation which has
> been removed with the rework of scheduler/cpufreq interface.
> This is wrong because sugov_effective_cpu_perf() already takes care of
> mapping the utilization to a performance level.
> 
> Fixes: 1b600da51073 ("PM: EM: Optimize em_cpu_energy() and remove division")
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
>   include/linux/energy_model.h | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
> index 770755df852f..70cd7258cd29 100644
> --- a/include/linux/energy_model.h
> +++ b/include/linux/energy_model.h
> @@ -245,7 +245,6 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
>   	 * max utilization to the allowed CPU capacity before calculating
>   	 * effective performance.
>   	 */
> -	max_util = map_util_perf(max_util);
>   	max_util = min(max_util, allowed_cpu_cap);
>   
>   	/*

LGTM. It was developed in parallel IIRC and that change which removes
the extra margin to the util was lost from my radar. I can see it
landed first.

Reviewed-by: Lukasz Luba <lukasz.luba@....com>

Regards,
Lukasz