This question already has an answer here:
I.e. is it the O(1) scheduler, the CFS scheduler, or an older one?
The scheduler of a process can be defined by the programmer, using this funcion man sched_setscheduler
to see the scheduler uses by a process you can use the top command
for change the scheduler of a procces chrt
You can call
I'm not sure how you could distinguish the O(1) scheduler from other obsolete schedulers. You could use the kernel version I suppose, but since distributions applied patches to their shipped kernels, this will be unreliable.