LRU is better than FIFO

In the paging problem we have to manage a two-level memory system, in which the first level has short access time but can hold only up to k pages, whi le the second level is very large but slow. We use competitive analysis to study the relative performance of the two best known algorithms for paging, LRU and FIFO. Sleator and Tarjan proved that the competitive ratio of LRU and FIFO is k. In practice, however, LRU is known to perform much better th an FIFO. It is believed that the superiority of LRU can be attributed to lo cality of reference exhibited in request sequences. In order to study this phenomenon, Borodin et al. [2] refined the competitive approach by introduc ing the concept of access graphs. They conjectured that the competitive rat io of LRU on each access graph is less than or equal to the competitive rat io of FIFO. We prove this conjecture in this paper.