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

[Wanghui (John)]

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