An Analysis of Degenerate Sharing and False Coherence Page 1 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 has been that no satisfactory definition for this problem exists. In this 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. Finally, we provide a counter intuitive example demonstrating that the elimination of degenerate sharing can reduce performance.