Question

A process has been allocated 3 page frames. Assume that none of the pages of the process are avaialable in the memory initially. The process makes the following sequence of page reference(reference string) : 1, 2, 1, 3, 7, 4, 5, 6, 3, 1.

Least Recently Used (LRU) page replacement policy is a practical approximation to optimal page replacenent. For the above reference string, how many more page fautls occur with LRU than with the optimal page replacement policy?

• A. 0
• B. 2
• C. 1
• D. 3

Answer 1

The correct option is B 2

Consider the LRU page replacement policy

So total number of page fault = 9
Number of page fault in LRU - Number of page
fault in optional = 9 - 7 = 2 more page fault.