Os Memory Management Questions Medium
The LRU-8 (Least Recently Used with 8th Chance) page replacement algorithm is a variation of the LRU (Least Recently Used) algorithm used in operating system memory management. It aims to minimize the number of page faults by evicting the least recently used pages from memory.
The working of the LRU-8 algorithm involves maintaining a list or queue of pages in memory, ordered based on their recent usage. Each page has a reference bit associated with it, which is initially set to 0. When a page is accessed, its reference bit is set to 1.
When a page fault occurs and there is no free frame available in memory, the algorithm selects a page to evict. It starts by examining the first page in the list. If its reference bit is 0, indicating that it has not been recently used, it is selected for eviction. The page is then removed from memory, and the new page is brought in its place.
However, if the reference bit of the first page is 1, it means that the page has been recently used. In this case, the algorithm gives the page another chance by setting its reference bit to 0 and moving it to the end of the list. This process is repeated for each page in the list until a page with a reference bit of 0 is found or the end of the list is reached.
The LRU-8 algorithm introduces an additional feature to handle pages that have been given multiple chances. When a page is moved to the end of the list for the 8th time, its reference bit is not reset to 0. Instead, it is evicted from memory, regardless of its reference bit value. This ensures that pages that have been given multiple chances are eventually evicted, allowing for better utilization of memory.
Overall, the LRU-8 algorithm combines the principles of the LRU algorithm with the concept of giving pages multiple chances before eviction. This helps in improving the efficiency of memory management by evicting the least recently used pages while also considering the frequency of their recent usage.