Question

Consider the following set of processes that need to be scheduled on a single CPU. All the times are given in milliseconds.

Process Name	Arrival Time	Execution Time
A	0	6
B	3	2
C	5	4
D	7	6
E	10	3

 

Using the shortest remaining time first scheduling algorithm, the average process turnaround time (in msec) is ______

Answer 1

Scheduling Algorithm: Shortest Remaining Time First (Pre-emptive)

Gantt chart:

A

B

A

C

E

D

0       3        5        8       12      15      21

Formula:

Turnaround time = Completion time – Arrival time.

Process Table:

Process Name	Arrival Time (AT)	Execution Time (ET)	Completion Time (CT)	Turnaround time (TAT)
A	0	6	8	8
B	3	2	5	2
C	5	4	12	7
D	7	6	21	14
E	10	3	15	5

 

Average turnaround time = \(\frac{{\left( {8\; + \;2\; + \;7\; + \;14\; + \;5} \right)}}{5} = 7.2\;msec\)

Important Points:

TAT = CT - AT