SMG: Shared Memory for Grids

J.P. Ryan and B.A. Coghlan (Ireland)


DSM, MPI, OpenMP, Grid, Incremental Hybridization


This paper discusses some of the salient issues involved in implementing the illusion of a shared-memory program ming model across a group of distributed memory proces sors from a cluster through to an entire Grid. This illusion can be provided by a distributed shared memory (DSM) runtime system. Mechanisms that have the potential to increase the perfor mance by minimizing high-latency intra site messages & data transfers are highlighted. Relaxed consistency mod els are investigated, as well as the use of a grid informa tion system to ascertain topology information. The latter allows for hierarchy-aware management of shared data and synchronization variables. The process of incremental hy bridization is also explored, where more efficient message passing mechanisms can incrementally replace DSM ac tions when circumstances dictate that performance im provements can be obtained. In this paper we describe the overall design/architecture of a prototype system, SMG, which integrates DSM and message passing paradigms and may be the target of an OpenMP compiler. Our initial findings based on some triv ial examples indicate some of the potential benefits that can be obtained for grid Applications.

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