This was an exam question I could not solve, even after searching about response time.
I thought that answer should be 220, 120
Effectiveness of RR scheduling depends on two factors: choice of q, the time quantum, and the scheduling overhead s. If a system contains n processes and each request by a process consumes exactly q seconds, the response time (rt) for a request is rt= n(q+s) . This means that response is generated after spending the whole CPU burst and being scheduled to the next process. (after q+s)
Assume that an OS contains 10 identical processes that were initiated at the same time. Each process contains 15 identical requests, and each request consumes 20msec of CPU time. A request is followed by an I/O operation that consumes 10 sec. The system consumses 2msec in CPU scheduling. Calculate the average reponse time of the fisrt requests issued by each process for the following two cases:
(i) the time quantum is 20msec.
(ii) the time quantum is 10 msec.