Application-Controlled Paging for a Shared Cache (Extended Abstract)

W e consider a cache shared by several concurrently running application processes and propose a provably efficient application-controlled global strategy for the shared cache. Using future information implicitly in the form of good decisions by application processes, we are able to break through the Hk lower bound on competitive ratio proved for classical paging for a k-sized cache in [FKL+91]. For a size-k cache shared by P application processes that always make good cache replacement decisions, we develop an online application-controlled paging algorithm with a competitive ratio of 2Hp-142. Typically, P is much smaller than k , perhaps by several orders of magnitude. Our competitive ratio improves upon the 2P + 2 competitive ratio achieved by [CFLSda]. W e show for this problem that no online algorithm A can have a competitive ratio better than Hp-1 even i f the application processes aiding A have perfect knowledge of individual request sequences. Our results are with respect to a worst-case interleaving of the individual request sequences of the P applications. W e introduce a notion of fairness in the more realistic situation when application processes do not always make good cache replacement deci"Support was provided in part by Army Research Office grant DAAH04-93-G-0076. +Supported in part by the National Science Foundation under grant CCR-9007851 and by the Air Force Office of Scientific Research grants F49620-92-5-0515 and F49620-94-1-0217. 0272-5428/95 $04.00