Linux : how to get avg time and turnaround time using Completely Fair Scheduler

I am working in a Completely fair scheduler which is the default scheduler in Linux (fair. c). I am trying to find out the avg waiting time and avg turnaround time using the default scheduler. Initially, I planned to write a separate prog that uses the default scheduler and gives the avg times. But now I am not sure how to implement it. Is there any way to get the avg time using the CFS scheduler?