† International Business Machines Corp.

Prefetching in shared-memory multiprocessor systems is an increasingly difficult problem. As system designs grow to incorporate larger numbers of faster processors, memory latency and interconnect traffic increase. While aggressive prefetching techniques can mitigate the increasing memory latency, they can harm performance by wasting precious interconnect bandwidth and prematurely accessing shared data, causing state downgrades at remote nodes that force later upgrades. This paper investigates Stealth Prefetching, a new technique that utilizes information from Coarse-Grain Coherence Tracking (CGCT) for prefetching data aggressively, stealthily, and efficiently in a broadcast-based shared-memory multiprocessor system. Stealth Prefetching utilizes CGCT to identify regions of memory that are not shared by other processors, aggressively fetches these lines from DRAM in open-page mode, and moves them close to the processor in anticipation of future references. Our analysis with commercial, scientific, and multiprogrammed workloads show that Stealth Prefetching provides an average speedup of 20 % over an aggressive baseline system with conventional prefetching