Adaptive migratory scheme for distributed shared memory

This paper presents an adaptive migratory scheme for software Distributed Shared Memory (DSM). The proposed DSM system allows each node to independently choose one of the following three protocols: migratory, invalidate, and competitive update. In software DSM systems the migratory protocol is not necessarily optimal for a migratory access pattern. We define some conditions under which the migratory protocol is to be preferred over other candidate protocols. In our scheme, each node independently and continuously collects statistics that are used to determine the protocol to be used for each local copy of a page. Different nodes may select different protocols for the same page, based on their local view of the memory access patterns. The proposed scheme is an improvement over our previous adaptive scheme [9] that allowed only invalidate and competitive update protocols. The proposed scheme is implemented on a workstation cluster. Experimental results show that the new scheme is able to improve performance by choosing migratory protocol when appropriate.