Shared-Memory Multiprocessors

The Psyche project at the University of Rochester aims to develop a high performance operating system to support a wide variety of models for parallel programming on a shared-memory multiprocessor. It is predicated on the assumption that no one model of process state or style of communication will prove appropriate for all applications, but that a shared-memory machine can and should support all models. Conventional approaches, such as shared memory or message passing, can be regarded as points on a continuum that reflects the degree of sharing between processes. Psyche enables fully dynamic sharing by providing a user interface based on passive data abstractions in a uniform virtual address space. It ensures that users pay for protection only when it is required by permitting lazy evaluation of protection using keys and access lists. The data abstractions define conventions for sharing the uniform address space; the tradeoff between protection and performance determines the degree to which those conventions are enforced. In the absence of protection boundaries, access to a shared abstraction can be as efficient as a procedure call or a pointer dereference