A process has been allocated 3-page frames. Assume that none of the pages of…
2007
A process has been allocated 3-page frames. Assume that none of the pages of the process are available in the memory initially. The process makes the following sequence of page references (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 replacement. For the above reference string, how many more page faults occur with LRU than with the optimal page replacement policy?
- A.
0
- B.
1
- C.
2
- D.
3
Attempted by 12 students.
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Correct answer: C
For Optimal policy, faults occur at references 1, 2, 3, 7, 4, 5, and 6 totaling 7 faults. For LRU policy, faults occur at every reference except the initial hits on 1 and 3 totaling 9 faults. The difference between LRU and Optimal page faults is exactly two.
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