Constructive and adaptable distributed shared memory

Abstract

Distributed shared memory (DSM) is a paradigm for programming distributed systems, which provides an alternative to the message passing model. DSM offers the agents of the system a shared address space through which they can communicate with each other. The main problem of a DSM implementation on top of a message passing system is performance. Performance of an implementation is closely related to the consistency the DSM system offers: strong consistency (all agents agree about how memory events happen) and is more expensive to implement than weak consistency (disagreements are allowed). There have been many DSM systems proposals, each one supporting different consistency levels. Experience has shown that no one is well suited for the whole range of problems. In some cases, strong consistent primitives are not needed, while in other cases, the weak semantics provided are useless. This is also true for different implementations of the same memory model, since performance is also affected by the data access patterns of the applications. We introduce a novel DSM model called Mume. Mume is a low level layer close to the level of the message passing interface. The Mume interface provides only the minimum requirements to be considered as a shared memory system. The interface includes three types of synchronization primitives, namely total ordering, causal ordering and mutual exclusion. This allows efficient implementations of different memory access semantics, accommodating particular data access patterns.