Os Memory Management Questions Medium
The LRU-K-WSR (Least Recently Used with K Working Set Replacement) page replacement algorithm is a variation of the LRU (Least Recently Used) algorithm that takes into account the concept of working sets.
In the LRU-K-WSR algorithm, each page in memory is associated with a counter that keeps track of the number of references made to that page. When a page needs to be replaced, the algorithm selects the page with the lowest counter value, indicating that it has been least recently used.
However, the LRU-K-WSR algorithm also considers the concept of working sets, which are defined as the set of pages that have been referenced within a specific time interval called the working set window. The working set window is typically defined in terms of the number of page references.
The algorithm maintains a working set table that keeps track of the working set size for each page. When a page is referenced, its counter is incremented, and if the page is not already in the working set table, it is added with a working set size of 1. If the page is already in the working set table, its working set size is incremented.
When a page needs to be replaced, the algorithm first checks if the page is in the working set table. If it is, the page is not eligible for replacement. If the page is not in the working set table, the algorithm selects the page with the lowest counter value, similar to the LRU algorithm.
The LRU-K-WSR algorithm also includes a working set replacement policy. If the working set size of a page exceeds the value of K, the page is considered to be part of the working set and is not eligible for replacement. This policy ensures that frequently referenced pages are not replaced, even if they have not been recently used.
Overall, the LRU-K-WSR algorithm combines the concepts of LRU and working sets to provide a more efficient page replacement strategy. It takes into account both recent usage and the working set size of pages to make intelligent decisions on which pages to replace, ultimately improving the overall performance of the memory management system.