linux-kernel - Re: [PATCH v2 1/2] sched/schedutil: rework performance estimation

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Date:   Thu, 2 Nov 2023 13:03:32 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com, rostedt@...dmis.org,
        bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com,
        vschneid@...hat.com, rafael@...nel.org, viresh.kumar@...aro.org,
        qyousef@...alina.io, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Cc:     lukasz.luba@....com, wyes.karny@....com, beata.michalska@....com
Subject: Re: [PATCH v2 1/2] sched/schedutil: rework performance estimation

On 26/10/2023 19:09, Vincent Guittot wrote:

[...]

> @@ -153,14 +152,38 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
>  	return cpufreq_driver_resolve_freq(policy, freq);
>  }
>  
> +unsigned long sugov_effective_cpu_perf(int cpu, unsigned long actual,
> +				 unsigned long min,
> +				 unsigned long max)
> +{
> +	unsigned long target;
> +	struct rq *rq = cpu_rq(cpu);
> +
> +	if (rt_rq_is_runnable(&rq->rt))
> +		return max;
> +
> +	/* Provide at least enough capacity for DL + IRQ */
> +	target = min;
> +
> +	actual = map_util_perf(actual);
> +	/* Actually we don't need to target the max performance */
> +	if (actual < max)
> +		max = actual;
> +
> +	/*
> +	 * Ensure at least minimum performance while providing more compute
> +	 * capacity when possible.
> +	 */
> +	return max(target, max);

The superfluous `unsigned long target` is still there?

  return max(min, max) is much cleaer.

[...]