GATE CSE 1995 | Question: 2.6

Question

The sequence __________ is an optimal non-preemptive scheduling sequence for the following jobs which leaves the CPU idle for ________ unit(s) of time.$$\small \begin{array}{|c|c|c|} \hline  \textbf{Job} & \textbf{Arrival Time} & \textbf{Burst Time} \\\hline 1 & 0.0 & 9 \\\hline  2 & 0.6 & 5 \\\hline 3 & 1.0 & 1 \\\hline \end{array}$$

• A. $\{3, 2, 1\}, 1$
• B. $\{2, 1, 3\}, 0$
• C. $\{3, 2, 1\}, 0$
• D. $\{1, 2, 3\}, 5$

Answer 1

SJF is best among all non-preemptive methods with its disadvantages. SJF gives less average waiting time and less Turn around time than others and more

in all scheduling algorithms SRJF(i.e SJF with preemption )gives optimal av. waiting time and av. Turn around time

So we will use SJF here to get optimal

3,2,1 will be the sequence but from 0 to 1 CPU will be idle

Comments

But if in sjf we don't have any idle time as here the first process arrives immediately at 0s so if we use sfj algo we should be processing job S1 instead we are creating an optimal sequence of our own