Why the implementation of optimal page replacement algorithm is difficult with respect to others algorithms?

Optimal Page Replacement algorithm is the best page replacement algorithm as it gives the least number of page faults. This algorithm was introduced long back and is difficult to implement because it requires future knowledge of the program behaviour.

What are the disadvantages of optimal page replacement algorithm?

Disadvantages of Optimal Replacement Algorithm are as follows:

• Not all operating systems can implement this algorithm.
• Error detection is harder.
• Least recently used page will be replaced which may sometimes take a lot of time.

What is true about optimal page replacement algorithm?

Explanation: Optimal page replacement algorithm has the lowest fault rate as it has the knowledge of all the pages beforehand. Explanation: Optimal page replacement algorithm is also called a Clairvoyant replacement algorithm or Belady’s optimal replacement algorithm.

Which page replacement algorithm is best?

LRU resulted to be the best algorithm for page replacement to implement, but it has some disadvantages. In the used algorithm, LRU maintains a linked list of all pages in the memory, in which, the most recently used page is placed at the front, and the least recently used page is placed at the rear.

Why page replacement algorithm is used?

Page replacement algorithms are an important part of virtual memory management and it helps the OS to decide which memory page can be moved out, making space for the currently needed page. However, the ultimate objective of all page replacement algorithms is to reduce the number of page faults.

Which page replacement algorithm cause more page fault with more page frames?

Belady’s anomaly – Belady’s anomaly proves that it is possible to have more page faults when increasing the number of page frames while using the First in First Out (FIFO) page replacement algorithm.

How does optimal page replacement algorithm select the next page?

Explanation: The optimal page replacement algorithm will select the page whose next occurrence will be after the longest time in future.

Why is LRU a good approximation of the optimal replacement algorithm?

A good approximation to the optimal algorithm is based on the observation that pages that have been heavily used in the last few instructions will probably be heavily used again in the next few. This strategy is called LRU (Least Recently Used) paging. …

Why the least recently used LRU algorithm is generally not used as a page replacement algorithm?

Although LRU is theoretically realizable, it is not cheap. To fully implement LRU, it is necessary to maintain a linked list of all pages in memory, with the most recently used page at the front and the least recently used page at the rear. The difficulty is that the list must be updated on every memory reference.