Consider the data given in above question.
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
Answer: (C)
Explanation: LRU replacement policy: The page that is least recently used is being Replaced.
Given String: 1, 2, 1, 3, 7, 4, 5, 6, 3, 1
123 // 1 ,2, 3 //page faults
173 ->7
473 ->4
453 ->5
456 ->6
356 ->3
316 ->1
Total 9
In http://quiz.geeksforgeeks.org/gate-gate-cs-2007-question-82/, In optimal Replacement total page faults=7
Therefore 2 more page faults
Answer is C
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