FPGA implementation of simplified Fuzzy LRU replacement algorithm

Abstract

The Least Recently Used (LRU) policy is often used as a page replacement algorithm for virtual memory, and it is considered to be good. The major problem is that it is time consuming algorithm. This paper presents an efficient hardware FPGA implementation for LRU algorithm based on fuzzy logic with reduced inference rules. In this proposal, the page's recency of reference is used as input crisp variable to calculate the fuzzy value. Then a knowledge base that composed of five inference rules are used to calculate the page replacement weights for the pages in the memory. These pages' weights are used to select the victim page for replacement when there is a page fault and no empty page frame available in the memory. All stages starting from the crisp input values until the decision of selection the victim page to be replaced is implemented using very careful designed FPGA circuits. The main features of the design are focusing on the time speed of decision and the FPGA area. That is done in two ways, reducing the fuzzy rules to five only and using the best of the FPGA capability. The results show that the merging between fuzzy logic and FPGA implementation is very promising to achieve the LRU page replacement algorithm in real time.