Re: [PATCH] [RFC] sched: restrict iowait boost for boosted task only

[Qais Yousef]

On 01/25/20 23:59, Qais Yousef wrote:
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 9b8916fd00a2..a76c02eecdaf 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -421,7 +421,8 @@ static unsigned long sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
>          * into the same scale so we can compare.
>          */
>         boost = (sg_cpu->iowait_boost * max) >> SCHED_CAPACITY_SHIFT;
> -       return max(boost, util);
> +       boost = max(boost, util);
> +       return uclamp_util_with(cpu_rq(sg_cpu->cpu), boost, NULL);
>  }
> 
>  #ifdef CONFIG_NO_HZ_COMMON

Forgot to mention this will work if the background task is the only task
running on this CPU. Like Quentin already pointed out, the iowait_boost might
need more massaging to allow finer per task control.

--
Qais Yousef