A Characterization of Scalable Shared Memories

The traditional consistency requirements of shared memory are expensive to provide both in large scale multiprocessor systems and also in distributed systems that implement a shared memory abstraction in software. As a result, several memory systems have been proposed that enhance performance and scalability of shared memories by providing weaker consistency guarantees. Often, different models are used to describe such memories which makes it difficult to relate and compare them. We develop a simple non-operational model and identify parameters that can be varied to describe not only the existing memories but also to identify new ones. We show how such a uniform framework makes it easy to compare and relate the various memories. We also use the model to show that a well known software solution to the critical section problem can be used to distinguish the RC[subscript sc] and RC[subscript pc] memories explored in the DASH architecture