Exploiting temporal and spatial constraints on distributed shared objects

Gigabit network technologies have made it possible to combine workstations into a distributed, massively-parallel computer system. Middleware, such as distributed shared objects (DSO), attempts to improve programmability of such systems, by providing globally accessible 'object' abstractions. Researchers have developed consistency protocols for replicated 'memory' objects. These protocols are well suited to scientific applications but less suited to multimedia or groupware applications. We address the state sharing needs of complex distributed applications with: high-frequency symmetric accesses to shared objects; unpredictable and limited locality of accesses; dynamically changing sharing behavior; and potential data races. We show that a DSO system exploiting application-level temporal and spatial constraints on shared objects can outperform shared object protocols which do not exploit application-level constraints. We compare our S(emantic) DSO against entry consistency using a sample application having the four properties mentioned above.