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Page Replacement Algorithms in Operating Systems

Difference Between LRU and FIFO Page Replacement Algorithms in Operating System

Last Updated : 07 Sep, 2023

Page replacement algorithms are used in operating systems to manage memory effectively. Page replacement algorithms are essential in operating systems for efficient memory management. These algorithms select which memory pages should be changed when a new page is brought. Least Recently Used (LRU) and First-In-First-Out (FIFO) are two popular page replacement algorithms.

LRU (Least Recently Used)

LRU keeps track of the page usage order based on the most recent access.
When a page fault occurs, the page that has been least recently used is replaced.
It requires additional data structures, such as a linked list or a priority queue, to maintain the order of page usage.
The LRU algorithm provides better performance by minimizing the number of page faults.
Read more about LRU page replacement.

FIFO (First-In-First-Out)

FIFO follows the simple principle of replacing the page that entered memory first.
When a page fault occurs, the oldest page, which arrived earliest, is replaced.
It does not require any additional data structures to maintain the order of page usage.
The FIFO algorithm is straightforward to implement but may not always provide optimal performance.
Read more about FIFO page replacement.

LRU vs FIFO

Differences	LRU	FIFO
Principle	Replaces the least recently used page	Replaces the oldest page in memory
Data Structure	Requires additional data structure for tracking page usage order	No additional data structure required
Performance	Performs better in reducing page faults	May not always provide optimal performance
Access Pattern Sensitivity	Sensitive to the access pattern of pages	Not sensitive to the access pattern
Implementation Complexity	Relatively more complex to implement	Simple to implement

Conclusion

Finally, the LRU and FIFO page replacement algorithms provide distinct strategies for memory management in operating systems. LRU prioritizes replacing the most recently used page while accounting for the temporal locality of page accesses. It requires additional data structure to keep track of page usage and, in general, performs better in terms of decreasing page faults. FIFO replaces the oldest page in memory on a first-in-first-out basis. It does not take into account the frequency of page usage and doesn't require additional data structures. FIFO, on the other hand, may not always deliver ideal performance.

Page Replacement Algorithms in Operating Systems

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