Temporal Prefetching Without the Off-Chip Metadata

Abstract

Temporal prefetching offers great potential, but this potential is difficult to achieve because of the need to store large amounts of prefetcher metadata off chip. To reduce the latency and traffic of off-chip metadata accesses, recent advances in temporal prefetching have proposed increasingly complex mechanisms that cache and prefetch this off-chip metadata. This paper suggests a return to simplicity: We present a temporal prefetcher whose metadata resides entirely on chip. The key insights are (1) only a small portion of prefetcher metadata is important, and (2) for most workloads with irregular accesses, the benefits of an effective prefetcher outweigh the marginal benefits of a larger data cache. Thus, our solution, the Triage prefetcher, identifies important metadata and uses a portion of the LLC to store this metadata, and it dynamically partitions the LLC between data and metadata.