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Subject: Re: [PATCH 4/2] sched/cpupri: Add CPUPRI_HIGHER
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        linux-kernel@vger.kernel.org
References: <20200922083934.19275-1-dietmar.eggemann@arm.com>
 <20201014195437.GD2974@worktop.programming.kicks-ass.net>
From:   Dietmar Eggemann <dietmar.eggemann@arm.com>
Message-ID: <17c8a9b5-b63a-1a1a-f11b-5e00c2a6ad34@arm.com>
Date:   Mon, 19 Oct 2020 16:15:01 +0200
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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@infradead.org>

[...]

> @@ -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@arm.com>