Consider the following set of processes arriving at time 0, with CPU burst time given in milliseconds (ms). Calculate the following using round robin scheduling algorithm with time quantum 4 ms.
(i) Average waiting time
(ii) Average turnaround time
| Process | CPU Burst Time (ms) |
|---------|--------------------|
| P1 | 24 |
| P2 | 3 |
| P3 | 3 |
Answer (1)
To solve this problem using the Round Robin scheduling algorithm with a time quantum of 4 ms, we must distribute the CPU burst times among the processes in a fair and cyclic manner. We'll begin by distributing CPU time in rounds, with each process getting up to 4 ms of CPU time in each round until all processes are completed.
Processes and CPU Burst Time:
P1: 24 ms
P2: 3 ms
P3: 3 ms
Round Robin Execution:
1st Round:
P1 executes for 4 ms (remaining 20 ms).
P2 executes for 3 ms (completed).
P3 executes for 3 ms (completed).
2nd Round:
P1 executes for 4 ms (remaining 16 ms).
3rd Round:
P1 executes for 4 ms (remaining 12 ms).
4th Round:
P1 executes for 4 ms (remaining 8 ms).
5th Round:
P1 executes for 4 ms (remaining 4 ms).
6th Round:
P1 executes for 4 ms (completed).
Completion times for processes:
P1 completes at 24 ms.
P2 completes at 7 ms.
P3 completes at 10 ms.
Turnaround Time Calculation: Turnaround time is the total time taken from process arrival to completion.
Turnaround time for P1 = 24 ms.
Turnaround time for P2 = 7 ms.
Turnaround time for P3 = 10 ms.
Average Turnaround Time = 3 24 + 7 + 10 = 3 41 ≈ 13.67 ms.
Waiting Time Calculation: Waiting time is the total time the process has been in the ready queue.
Waiting time for P1 = 24 - 24 = 0 ms.
Waiting time for P2 = 7 - 3 = 4 ms.
Waiting time for P3 = 10 - 3 = 7 ms.
Average Waiting Time = 3 0 + 4 + 7 = 3 11 ≈ 3.67 ms.
In summary, the average waiting time is approximately 3.67 ms, and the average turnaround time is approximately 13.67 ms for the given set of processes using Round Robin scheduling with a time quantum of 4 ms.
