Advantages and Disadvantages of various Page Replacement algorithms

Page Scheduling, involves many different algorithms which have their Advantages and Disadvantages.

1. First In First Out (FIFO):

  • Advantages –

    1. It is simple and easy to understand & implement.
  • Disadvantages –

    1. The process effectiveness is low.
    2. When we increase the number of frames while using FIFO, we are giving more memory to processes. So, page fault should decrease, but here the page faults are increasing. This problem is called as Belady’s Anomaly.
    3. Every frame needs to be taken account off.

2. Least Recently Used (LRU):

  • Advantages –

    1. It is open for full analysis.
    2. In this, we replace the page which is least recently used, thus free from Belady’s Anomaly.
    3. Easy to choose page which has faulted and hasn’t been used for a long time.
  • Disadvantages –

    1. It requires additional Data Structure to be implemented.
    2. Hardware assistance is high.

3. Optimal Page Replacement (OPR):

  • Advantages –

    1. Complexity is less and easy to implement.
    2. Assistance needed is low i.e Data Structure used are easy and light.
  • Disadvantages –

    1. OPR is perfect, but not possible in practice as the operating system cannot know future requests.
    2. Error handling is tough.

While FIFO and LRU have their share of advantages and disadvantages, OPR is used as a benchmark to measure the performance of other algorithms. So according to the situation appropriate algorithm is used.

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