Re: [PATCH 4/2] sched/cpupri: Add CPUPRI_HIGHER

[Dietmar Eggemann]

On 14/10/2020 21:54, Peter Zijlstra wrote:
> 
> Add CPUPRI_HIGHER above the RT99 priority to denote the CPU is in use
> by higher priority tasks (specifically deadline).

sugov:X already triggers this now on our !fast-switching devices running
schedutil.

> XXX: we should probably drive PUSH-PULL from cpupri, that would
> automagically result in an RT-PUSH when DL sets cpupri to CPUPRI_HIGHER.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

[...]

> @@ -54,6 +56,10 @@ static int convert_prio(int prio)

The BUG_ON could be tightened:

-       BUG_ON(prio >= MAX_PRIO);
+       BUG_ON(prio > MAX_RT_PRIO);

>  	case MAX_RT_PRIO-1:
>  		cpupri = CPUPRI_NORMAL;		/*  0 */
>  		break;
> +
> +	case MAX_RT_PRIO:
> +		cpupri = CPUPRI_HIGHER;		/* 100 */
> +		break;
>  	}
> 
>  	return cpupri;

Just saw that the comment for cpupri_set() needs changing:

@@ -205,7 +208,7 @@ int cpupri_find_fitness(struct cpupri *cp, struct
task_struct *p,
  * cpupri_set - update the CPU priority setting
  * @cp: The cpupri context
  * @cpu: The target CPU
- * @newpri: The priority (INVALID-RT99) to assign to this CPU
+ * @newpri: The priority (INVALID-RT1-RT99-NORMAL-HIGHER) to assign to
this CPU

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>