Experiences in integrating distributed shared memory with virtual memory management

While the duality between message-passing and shared memory for interprocess communication is well-known, the shared memory paradigm has drawn considerable attention in recent times even in distributed systems. Distributed Shared Memory (DSM) is the abstraction for supporting the notion of shared memory in a physically non-shared (distributed) architecture. It gives a uniform set of mechanisms for accessing local and remote memories. Further, by combining shared memory style synchronization with the actual data transport in the DSM design, it is possible to provide flexible sharing while assuring mutual exclusion when necessary. This research reports on our experience in implementing a DSM system in an object-based distributed operating system. The important observation from this experience is the need for a tight cooperation between the virtual memory management at each node and the mechanisms provided by the DSM. Such a cooperation is essential to assure good performance of the DSM mechanisms and make the shared memory paradigm viable in a distributed environment.