SCHED_OTHER : why min/max priority are both 0 ?

Question

Question 1:

There are 140 priorities and SCHED_OTHER can have proprieties between 100 to 140.

But the chrt command gives SCHED_OTHER min/max priority : 0/0 ! . I expected 100 to 140 (or 0 to 39). Why the priority is fixed as 0 ?

Question 2:

Is there any difference for SCHED_OTHER in O(1) and CFS in terns of priority level and nice value calculation ?

Answer 1

I got it here:

• sched_rt.c implements SCHED_FIFO and SCHED_RR semantics, in a simpler way than the vanilla scheduler does. It uses 100 runqueues (for all 100 RT priority levels, instead of 140 in the vanilla scheduler) and it needs no expired array.