Lecture Notes in Computer Science, 2007, Volume 4368/2007, 95-107, DOI: 10.1007/11970125_8

Theoretical Evidence for the Superiority of LRU-2 over LRU for the Paging Problem

Joan Boyar, Martin R. Ehmsen and Kim S. Larsen

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Abstract

The paging algorithm LRU-2 was proposed for use in data-base disk buffering and shown experimentally to perform better than LRU [O’Neil, O’Neil, and Weikum, 1993]. We compare LRU-2 and LRU theoretically, using both the standard competitive analysis and the newer relative worst order analysis. The competitive ratio for LRU-2 is shown to be 2k for cache size k, which is worse than LRU’s competitive ratio of k. However, using relative worst order analysis, we show that LRU-2 and LRU are asymptotically comparable in LRU-2’s favor, giving a theoretical justification for the experimental results.
This work was supported in part by the Danish Natural Science Research Council (SNF).

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