A Simulation-Based Comparison of Cache Replacement Policies under Different Workloads and Cache Sizes

The effectiveness of a cache replacement rule depends on the pattern of requests it receives and on how much space is available to retain previously requested items. This study used a deterministic simulator to compare least recently used (LRU), first-in-first-out (FIFO), and least frequently used (LFU) under three synthetic request patterns: uniform-random, Zipfian-skewed, and scan-heavy/mixed. For each workload, ten independently seeded traces of 50,000 requests were tested at capacities of 100, 250, 500, and 1,000 entries. The outcome was the proportion of requests served from the cache, reported as a mean and standard deviation across seeds. At capacity 500, LFU recorded the highest mean hit rate on the Zipfian workload (79.96% ± 0.22 percentage points), followed by LRU (75.88% ± 0.18) and FIFO (71.99% ± 0.19). On uniform-random requests, the three methods were almost indistinguishable, with hit rates of approximately 4.95% to 4.98%. In the specified scan-heavy/mixed workload, hit rates ranged from 4.12% to 4.56%. Larger caches generally improved hit rates, particularly under Zipfian access. These findings describe the behaviour of the stated simulator and input generators; they do not establish which policy will perform best in a production system. Tests using public application traces or a real storage workload are needed before making operational recommendations.