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

Peter Zijlstra
2019-01-22T15:21:32Z

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);