GATE - 2006 | OS | Consider three processes, all arriving at time zero, with total
Posted on 18-02-2022
GATE - 2006 [Operating System]
Question:
Consider three processes, all arriving at time zero, with total execution time of 10, 20 and 30 units, respectively. Each process spends the first 20% of execution time doing I/O, the next 70% of time doing computation, and the last 10% of time doing I/O again. The operating system uses a shortest remaining compute time first scheduling algorithm and schedules a new process either when the running process gets blocked on I/O or when the running process finishes its compute burst. Assume that all I/O operations can be overlapped as much as possible. For what percentage of time does the CPU remain idle?
|
A |
0% |
|
B |
10.6% |
|
C |
30.0% |
|
D |
89.4% |
Solution:
Option (B) is Correct.
Total time needed to complete the execution = 47
Idle time = 2+3 = 5
Percentage of Idle time = 5/47 × 100 =10.6%