Migrating-home protocol for software distributed shared memory

Abstract

The efficiency of Software Distributed Shared Memory (DSM) is often limited by the excessive amount of network communication in maintaining the memory consistency of the system. Two of the most popular software solutions to reduce redundant data traffic are relaxed memory consistency models and traffic-thrifty coherence protocols. In this paper, we propose the migrating-home protocol for a relaxed memory consistency model, the scope consistency model. The protocol allows the processor storing the most up-to-date copy of a page to change from one processor to another, so as to better adapt to the memory access patterns of DSM applications. The new protocol has been implemented in a DSM system running on a 16-node Pentium III 450MHz PC cluster. We analyzed not only the execution time of the benchmark programs, but also the communication and page fault patterns via a new analysis approach. It is shown that our DSM system reduces the amount of network communication and handles page faults more efficiently. The benchmark results provide concrete evidence for the substantial performance improvement obtained by our system.