From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v6 08/16] sched/cpufreq: uclamp: Add utilization clamping
 for FAIR tasks
Date: Tue, 22 Jan 2019 16:21:32 +0100
Message-ID: <20190122152132.GR27931@hirez.programming.kicks-ass.net>
References: <20190115101513.2822-1-patrick.bellasi@arm.com>
 <20190115101513.2822-9-patrick.bellasi@arm.com>
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To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-api@vger.kernel.org, Ingo Molnar <mingo@redhat.com>, Tejun Heo <tj@kernel.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Vincent Guittot <vincent.guittot@linaro.org>, Viresh Kumar <viresh.kumar@linaro.org>, Paul Turner <pjt@google.com>, Quentin Perret <quentin.perret@arm.com>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Morten Rasmussen <morten.rasmussen@arm.com>, Juri Lelli <juri.lelli@redhat.com>, Todd Kjos <tkjos@google.com>, Joel Fernandes <joelaf@google.com>, Steve Muckle <smuckle@google.com>, Suren Baghdasaryan <surenb@google.com>
List-Id: linux-api@vger.kernel.org

On Tue, Jan 15, 2019 at 10:15:05AM +0000, Patrick Bellasi wrote:
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -218,8 +218,15 @@ unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
>  	 * CFS tasks and we use the same metric to track the effective
>  	 * utilization (PELT windows are synchronized) we can directly add them
>  	 * to obtain the CPU's actual utilization.
> +	 *
> +	 * CFS utilization can be boosted or capped, depending on utilization
> +	 * clamp constraints requested by currently RUNNABLE tasks.
> +	 * When there are no CFS RUNNABLE tasks, clamps are released and
> +	 * frequency will be gracefully reduced with the utilization decay.
>  	 */
> -	util = util_cfs;
> +	util = (type == ENERGY_UTIL)
> +		? util_cfs
> +		: uclamp_util(rq, util_cfs);

That's pretty horrible; what's wrong with:

	util = util_cfs;
	if (type == FREQUENCY_UTIL)
		util = uclamp_util(rq, util);

That should generate the same code, but is (IMO) far easier to read.

>  	util += cpu_util_rt(rq);
>  
>  	dl_util = cpu_util_dl(rq);