• İhsan Doğramacı Bilkent University

• CS 342

Quiz 3 – Section 2

April 24, 2003, Thursday

Question

4 processes arrive to a system that uses Round Robin scheduling with quantum of 2

time units. The arrival times of each process and their required CPU time is given

below. Calculate their finish times and turnaround times. Assume each process is 100

percent CPU-bound.

Process Arrival Time Required CPU Time

0 0 10

1 3 6

2 5 8

3 9 8

Answer

Lets denote process 0 with A, process 1 with B, process 2 with C, and process 3 with D.

The figure below shows which process is using the Cpu at which times in detail. The

table below that shows events occuring in some time instances.

Time Event Ready Queue

State

0 A arrives A

2 A quantum expires A

3 B arrives A B

4 A quantum expires B A

4 B is scheduled B A

5 C arrives B A C

6 B quantum expires A C B

6 A isscheduled A C B

8 A quantum expires C B A

8 C is scheduled C B A

9 D arrives C B A D

10 C quantum expires B A D C