A Shared Memory Environment for Hypercubes

This paper describes the design and implementation of a shared virtual memory (SVM) system for the nCUBE 2 hypercube multicomputer. The SVM system provides the user a single coherent address space across all nodes. It is implemented at the user level in a C programming environment using high level constructs to support data sharing. Shared variables are treated as objects rather than pages. We have improved upon an existing algorithm for maintaining coherency in the SVM system, thus achieving a reduction in the number of inter-node messages required in coherency maintenance. Detailed timing analysis is conducted to analyze the feasibility of this shared environment. Experimental results indicate that parallel programs running under an SVM system show linear speedup, suggesting that SVM systems could provide an effective programming environment for the next generation of distributed memory parallel computers. A bottleneck of this implementation seems to be the expensive interrupt handling by the nCUBE 2 kernel.