GATE - 2015 | OS | For the processes listed in the following table, which of the following

GATE - 2015 [Operating System]

Question:

For the processes listed in the following table, which of the following scheduling schemes will give the lowest average turnaround time?

A	First Come First Serve
B	Non-preemptive Shortest Job First
C	Shortest Remaining Time
D	Round Robin with Quantum value two

   

Solution:

Option (C) is Correct.

FCFS:

TAT for A = completion time(A) - AT(A) = 3 - 0 = 3
TAT of B = 9 - 1 = 8
TAT of C = 13 - 4 = 9
TAT of D = 15 - 6 = 9
∴ Avg. TAT = 29/4

SJF:

TAT of A = 3 - 0 = 3
TAT of B = 9 - 1 = 8
TAT of C = 15 - 4 = 11
TAT of D = 11 - 6 = 5
∴ Avg. TAT = 27/4

SRTF:

TAT of A = 3 - 0 = 3
TAT of B = 15 - 1 = 14
TAT of C = 8 - 4 = 4
TAT of D = 10 - 6 = 4
∴ Avg. TAT = 25/4

RR:

TAT of A = 5 - 0 = 5
TAT of B = 15 - 1 = 14
TAT of C = 13 - 4 = 9
TAT of D = 11 - 6 = 5

∴ Avg. TAT = 33/4

∴ SRTF has the lowest Avg. TAT.

Thank You