Studying the impact of hardware prefetching and bandwidth partitioning in chip-multiprocessors
Fang Liu, Yan Solihin · 2011
Modern high performance microprocessors widely employ hardware prefetching technique to hide long memory access latency. While very useful, hardware prefetching tends to aggravate the bandwidth wall, a problem where system performance is increasingly limited by the availability of the off-chip pin bandwidth in Chip Multi-Processors (CMPs).In this paper, we propose an analytical model-based study to investigate how hardware prefetching and memory bandwidth partitioning impact CMP system performance and how they interact. The model includes a composite prefetching metric that can help determine under which conditions prefetching can improve system performance, a bandwidth partitioning model that takes into account prefetching effects, and a derivation of the weighted speedup optimum bandwidth partition sizes for different cores. Through model-driven case studies, we find several interesting observations that can be valuable for future CMP system design and optimization. We also explore simulation-based empirical evaluation to validate the observations and show that maximum system performance can be achieved by selective prefetching, guided by the composite prefetching metric, coupled with dynamic bandwidth partitioning.