linux-kernel - Re: [RFC 1/8] sched: Add nice value change notifier

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Message-ID: <562d45e1-4a27-3252-f615-3ab1ef531f2b@huawei.com>
Date:   Wed, 6 Oct 2021 12:10:19 +0800
From:   "Wanghui (John)" <john.wanghui@...wei.com>
To:     Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        <Intel-gfx@...ts.freedesktop.org>
CC:     <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [RFC 1/8] sched: Add nice value change notifier

HI Tvrtko

On 2021/10/4 22:36, Tvrtko Ursulin wrote:
>   void set_user_nice(struct task_struct *p, long nice)
>   {
>   	bool queued, running;
> -	int old_prio;
> +	int old_prio, ret;
>   	struct rq_flags rf;
>   	struct rq *rq;
>   
> @@ -6915,6 +6947,9 @@ void set_user_nice(struct task_struct *p, long nice)
>   
>   out_unlock:
>   	task_rq_unlock(rq, p, &rf);
> +
> +	ret = atomic_notifier_call_chain(&user_nice_notifier_list, nice, p);
> +	WARN_ON_ONCE(ret != NOTIFY_DONE);
>   }
How about adding a new "io_nice" to task_struct，and move the call chain to
sched_setattr/getattr, there are two benefits:

1. Decoupled with fair scheduelr. In our use case, high priority tasks often
    use rt scheduler.
2. The range of value don't need to be bound to -20~19 or 0~139