Dynamic Data Prefetching in Home-Based Software DSMs

A major overhead in software DSM (Distributed Shared Memory) is the cost of remote memory accessesnecessitated by the protocol as well as induced by false sharing. This paperintroduces a dynamic prefetching method implemented in the JIAJIA software DSMto reduce system overhead caused by remote accesses. The prefetchingmethod records the interleaving string of INV (invalidation) and GETP (getting aremote page) operations for each cached page and analyzes the periodicity ofthe string when a page is invalidated on a lock or barrier. A prefetchingrequest is issued after the lock or barrier if the periodicity analysisindicates that GETP will be the next operation in the string. Multipleprefetching requests are merged into the same message if they are to the samehost. Performance evaluation with eight well-accepted benchmarks in a cluster ofsixteen PowerPC workstations shows that the prefetching scheme can significantlyreduce the page fault overhead and as a result achieves a performanceincrease of 15%--20% in three benchmarks and around 8%--10% inanother three. The average extra traffic caused by uselessprefetches is only 7%--13% in the evaluation.