Question

The main memory can hold 3-page frames and initially, all of them are vacant. Consider the following stream of page requests: 2, 3, 2, 4, 6, 2, 5, 6, 1, 4, 6 If the stream uses FIFO replacement policy, the hit ratio h will be
1. 11 / 3
2. 1 /11
3. 3 / 11
4. 2 / 11

Answer 1

Correct Answer - Option 4 : 2 / 11

Concept:

1). In FIFO Replacement Algorithm, the selected page is replaced with one that has been in memory for the longest time (the oldest page).

2). Hit Ratio = \( \frac{Total~HIts}{Total~Accesses}\)

Analysis:

2	3	2	4	6	2	5	6	1	4	6
2	2	2	2	6	6	6	6	1	1	1
	3	3	3	3	2	2	2	2	4	4
			4	4	4	5	5	5	5	6
M	M	H	M	M	M	H	M	M	M	M

 

M = Miss (9)

H = Hit (2)

∴ The hit ratio will be:

\( \frac{Total~HIts}{Total~Accesses}~=~\frac{2}{9~+~2}\)

Hit Ratio \( =~\frac{2}{11}\)