Replacement Algorithm Improved on 2Q~* for Mail Service Workload and its Application in Storage Cache

This paper analyzed the performance characteristics of classic 2Q algorithm when it was performed on mail-service workloads,and proposed an improved algorithm,called 2Q*.The simulation results show that 2Q* algorithm can outperform the other replacement algorithms,including the classic 2Q algorithm,for all the cache sizes and various mail-service workloads.To verify the simulation results in real practice,we implemented the algorithm in FlexiCache,a partitioned buffer cache system,and integrated it with a popular adaptive sequential prefect policy properly.The experiment results in real system further confirm the effectiveness of 2Q* algorithm for mail service kind of applications in improving their physical I/O performance.Moreover,its runtime overhead is also fairly low.