linux-kernel - Re: [PATCH 3/6] sched: Allow sched_{get,set}attr to change latency

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Message-ID: <6bee2e39-34a8-905f-084f-379b8476ea98@arm.com>
Date:   Mon, 28 Mar 2022 11:23:46 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com, rostedt@...dmis.org,
        bsegall@...gle.com, mgorman@...e.de, linux-kernel@...r.kernel.org,
        parth@...ux.ibm.com
Cc:     qais.yousef@....com, chris.hyser@...cle.com,
        pkondeti@...eaurora.org, valentin.schneider@....com,
        patrick.bellasi@...bug.net, David.Laight@...lab.com,
        pjt@...gle.com, pavel@....cz, tj@...nel.org,
        dhaval.giani@...cle.com, qperret@...gle.com,
        tim.c.chen@...ux.intel.com
Subject: Re: [PATCH 3/6] sched: Allow sched_{get,set}attr to change
 latency_nice of the task

On 11/03/2022 17:14, Vincent Guittot wrote:

[...]

> @@ -98,6 +99,22 @@ struct sched_param {
>   * scheduled on a CPU with no more capacity than the specified value.
>   *
>   * A task utilization boundary can be reset by setting the attribute to -1.
> + *
> + * Latency Tolerance Attributes
> + * ===========================
> + *
> + * A subset of sched_attr attributes allows to specify the relative latency
> + * requirements of a task with respect to the other tasks running/queued in the
> + * system.
> + *
> + * @ sched_latency_nice	task's latency_nice value
> + *
> + * The latency_nice of a task can have any value in a range of
> + * [LATENCY_NICE_MIN..LATENCY_NICE_MAX].

s/LATENCY_NICE_MIN/MIN_LATENCY_NICE
s/LATENCY_NICE_MAX/MAX_LATENCY_NICE

> + * A task with latency_nice with the value of LATENCY_NICE_MIN can be
> + * taken for a task with lower latency requirements as opposed to the task with
> + * higher latency_nice.

low latency nice (priority): -20 -> high weight: 1024 ... Doesn't a task
with MIN_LATENCY_NICE -20 have the highest latency requirements?

[...]