LRU Page Replacement Algorithm
Page
replacement algorithm are needed to decide which page to be replaced when new page
comes in main memory. Page Fault – A page
fault occurs when a program attempts to access a block of memory that is
not stored in the physical memory, or RAM. Different page replacement
algorithms are: FIFO, LRU, Optimal. The target for all algorithms
is to reduce number of page faults.
LRU Stands for Least Recently Used. In Least Recently Used (LRU) algorithm is a Greedy algorithm where the page to be replaced is least recently used. The LRU algorithm can be implemented by associating a counter with every page that is in main memory. When a page is referenced, its associated counter is set to 0. At fixed intervals of time, the counters associated with all pages presently in memory are incremented by 1. The least recently used page is the page with the highest count. The counters are often called aging registers, as their count indicates their age, that is, how long their associated pages have been referenced.
Advantages
Performance
of LRU is high in compare to FIFO.
Disadvantage
Maintain
a counter for each page.
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