Re: [PATCH v6 08/16] sched/cpufreq: uclamp: Add utilization clamping for FAIR tasks

[Peter Zijlstra]

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);