AN ANALYSIS OF DEGENERATE SHARING AND FALSE COHERENCE

False sharing reduces system performance in distributed shared memory systems. A major impediment to solving the problem of false sharing ha s been that no satisfactory definition for this problem exists. In thi s paper we provide definitions for several types of degenerate sharing , including false sharing. We also provide an algorithm that computes the cost of unnecessary coherence (false coherence) in a shared memory system using a single memory trace. Finally, we provide a counterintu itive example demonstrating that the elimination of degenerate sharing can reduce performance. (C) 1996 Academic Press, Inc.