Page replacement algorithms

Page Replacement Algorithm


Q      What do you mean by page replacement algorithm ? Enlist different page replacement algorithms.                      ( May – 2017 )      ( Marks – 4 )

Ans.:-    When a page fault occurs, page replacement algorithms are used for loading the page in memory and no free page frame exist in memory.  Page fault occurs if a running process references a non resident page.

The goal of a replacement strategy is to minimize the fault rate. To evaluate a replacement algorithm, following parameters are used :

  1. The size of a page
  2.  A set of reference strings
  3. The number of page frames.

Given these inputs, we can determine the number of reference string is a list of pages in order of their reference by the processor. When we find that a page frame reference is in main memory then we have a page hit and when page fault occurs we say it is page miss. A poor choice of page replacement algorithm may result in lot of how the kernel decides which page reclaim. Operating systems selects the local or global page replacement policy, local replacement policy allocates a certain number of pages to each process. If a process needs new page, it must replace one of its own pages. If the OS uses a global policy, it can take a page form any process, using global selection criteria.

  • FIFO,
  • LRU,
  • Optimal


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Last modified: Friday, 20 September 2019, 10:41 AM