Division of Labor: A More Effective Approach to Prefetching

Prefetching is a central component in most microarchitectures. Many different algorithms have been proposed with varying degrees of complexity and effectiveness. There are inherent tradeoffs among various metrics especially when we try to exploit both simpler access patterns and more complex ones simultaneously. Hypothetically, therefore, it is better to have collaboration of sub-components each specialized in exploiting a different access pattern than to have a monolithic design trying to have a similar prefetching scope. In this paper, we present some empirical evidence. We use a few components dedicated for some simple patterns such as canonical strided accesses. We show that a composite prefetcher with these components can significantly out perform state-of-the-art prefetchers. But more importantly, the composite prefetcher achieves better performance through a more limited prefetching scope while attaining a much higher accuracy. This suggests that the design can be more readily expanded with additional components targeting other patterns.