linux-kernel - Re: [PATCH 6/8] cpufreq/schedutil: sum per-sched class utilization

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Message-ID: <20160315212926.GG6344@twins.programming.kicks-ass.net>
Date:	Tue, 15 Mar 2016 22:29:26 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michael Turquette <mturquette@...libre.com>
Cc:	rjw@...ysocki.net, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, Juri.Lelli@....com,
	steve.muckle@...aro.org, morten.rasmussen@....com,
	dietmar.eggemann@....com, vincent.guittot@...aro.org,
	Michael Turquette <mturquette+renesas@...libre.com>
Subject: Re: [PATCH 6/8] cpufreq/schedutil: sum per-sched class utilization

On Sun, Mar 13, 2016 at 10:22:10PM -0700, Michael Turquette wrote:

> +static unsigned long sugov_sum_total_util(struct sugov_cpu *sg_cpu)
> +{
> +	enum sched_class_util sc;
> +
> +	/* sum the utilization of all sched classes */
> +	sg_cpu->total_util = 0;
> +	for (sc = 0; sc < nr_util_types; sc++)
> +		sg_cpu->total_util += sg_cpu->util[sc];
> +
> +	return sg_cpu->total_util;
> +}

> @@ -153,7 +172,7 @@ static unsigned int sugov_next_freq(struct sugov_policy *sg_policy,
>  		if ((s64)delta_ns > NSEC_PER_SEC / HZ)
>  			continue;
>  
> -		j_util = j_sg_cpu->util;
> +		j_util = j_sg_cpu->total_util;
>  		j_max = j_sg_cpu->max;
>  		if (j_util > j_max)
>  			return max_f;

So while not strictly wrong, I think we can do so much better.

Changelog doesn't mention anything useful, like that this is indeed very
rough and what we really should be doing etc..