Question

Consider the set of processes with arrival time (in milliseconds), CPU burst time (in milliseconds), and priority (0 is the highest priority) shown below. None of the processes have I/O burst time.

Process	Arrival Time	Burst Time	Priority
$P_1$	0	11	2
$P_2$	5	28	0
$P_3$	12	2	3
$P_4$	9	10	1
$P_5$	9	16	4

The average waiting time (in milliseconds) of all the processes using preemptive priority sccheduling algorithm is _____.

Answer 1

Process	Arrival Time	Burst Time	Priority	C.T.	T.A.T.	W.T.
$P_1$	0	11	2	49	49	38
$P_2$	5	28	0(high)	33	28	0
$P_3$	12	2	3	51	39	37
$P_4$	2	10	1	40	38	28
$P_5$	9	16	4	67	58	42

Total

145

$P_1$

$P_4$

$P_2$

$P_4$

$P_1$

$P_3$

$P_5$

0 2 5 33 40 49 51 67

Average waiting time $=\frac{145}{9}=29$