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GATE question on Belady's Anomaly

 

GATE: 2016: Q. 20

In which one of the following page replacement algorithms is possible for the page fault rate to increase even when the number of allocated frames increases?

A. LRU (Least Recently Used)

B. OPT (Optimal Page Replacement)

C. MRU (Most Recently Used)

D. FIFO (First In First Out)

 

Solution:

To achieve the desirable page fault i.e. page fault decreases as the number of frames increases (inversely proportionate), a page replacement algorithm must follow the stack property (also called the inclusion property).

 

So, if any page replacement algorithm does not follow stack property, then Belady’s anomaly occurs. 

But FIFO does not follow stack property this is the reason Belady’s occurs in FIFO.

 

For more detail please follow chapter: Stack Property

 

So, option (D) is correct.