linux-kernel - Re: [PATCH v6 2/2] cpuidle: teo: Introduce util-awareness

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Date:   Tue, 11 Jul 2023 18:58:14 +0100
From:   Qais Yousef <qyousef@...alina.io>
To:     Kajetan Puchalski <kajetan.puchalski@....com>
Cc:     rafael@...nel.org, daniel.lezcano@...aro.org, lukasz.luba@....com,
        Dietmar.Eggemann@....com, dsmythies@...us.net,
        yu.chen.surf@...il.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/2] cpuidle: teo: Introduce util-awareness

Hi Kajetan

On 01/05/23 14:51, Kajetan Puchalski wrote:

[...]

> @@ -510,9 +598,11 @@ static int teo_enable_device(struct cpuidle_driver *drv,
>  			     struct cpuidle_device *dev)
>  {
>  	struct teo_cpu *cpu_data = per_cpu_ptr(&teo_cpus, dev->cpu);
> +	unsigned long max_capacity = arch_scale_cpu_capacity(dev->cpu);
>  	int i;
>  
>  	memset(cpu_data, 0, sizeof(*cpu_data));
> +	cpu_data->util_threshold = max_capacity >> UTIL_THRESHOLD_SHIFT;

Given that utilization is invariant, why do we set the threshold based on
cpu capacity?

I'm not sure if this is a problem, but on little cores this threshold would be
too low. Given that util is invariant - I wondered if we need to have a single
threshold for all type of CPUs instead. Have you tried something like that
while developing the patch?


Thanks

--
Qais Yousef