Belady’s anomaly occur while FIFO Page Replacement Policy - Operating System

Q.  Where can the Belady’s anomaly occur?
- Published on 27 Aug 15

a. LRU Page Replacement Policy
b. MRU Page Replacement Policy
c. Optimal Page Replacement Policy
d. FIFO Page Replacement Policy

ANSWER: FIFO Page Replacement Policy


  • Nirja Shah   -Posted on 12 Nov 15
    Bélády's anomaly
    - It is the name given to the phenomenon where increasing the number of page frames results in an increase in the number of page faults for a given memory access pattern.

    - It is mostly experienced while using the First in First Out (FIFO) page replacement algorithm.

    - It was demonstrated in 1969 by László Bélády.

    - The information is loaded in specific chunks using the common computer memory management.

    - Each chunk is referred to as a page.

    - At a time only limited pages can be held by the central processor.

    - A frame is required by each page to load.

    - A page fault occurs when a page is not found, and might need to be loaded from disk into memory.

    - Whenever a page fault occurs and all the frames are in use, one must be cleared to make space for the new page.

    - A simple algorithm is FIFO: whichever page has been in the frames the longest is the one that is cleared.

    - It was always believed that an increase in the number of page frames would always result in the same number or fewer bpage faults unless the Bélády's anomaly was demonstrated.

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