Question

Assume that there are 3 page frames which are initially empty. If the page reference string is 1, 2, 3, 4, 2, 1, 5, 3, 2, 4, 6, the number of page faults using the optimal replacement policy is__________.

Answer 1

Page reference: 1, 2, 3, 4, 2, 1, 5, 3, 2, 4, 6

Page replacement algorithm: optimal replacement policy

page references	1	2	3	4	2	1	5	3	2	4	6
Frames	1	1	1	1	2	5	5	3	3	3	6
		2	2	2	3	2	2	2	2	2	2
			3	4	4	4	4	4	4	4	4
Page status	M	M	M	M	H	H	M	M	H	H	M

 

Optimal = 7 miss = 7 page faults

Important Point:

M → miss

H → Hit