Inter-core cooperative TLB for chip multiprocessors

Abstract

Translation Lookaside Buffers (TLBs) are commonly employed in modern processor designs and have considerable impact on overall system performance. A number of past works have studied TLB designs to lower access times and miss rates, specifically for uniprocessors. With the growing dominance of chip multiprocessors (CMPs), it is necessary to examine TLB performance in the context of parallel workloads. This work is the first to present TLB prefetchers that exploit commonality in TLB miss patterns across cores in CMPs. We propose and evaluate two Inter-Core Cooperative (ICC) TLB prefetching mechanisms, assessing their effectiveness at eliminating TLB misses both individually and together. Our results show these approaches require at most modest hardware and can collectively eliminate 19% to 90% of data TLB (D-TLB) misses across the surveyed parallel workloads. We also compare performance improvements across a range of hardware and software implementation possibilities. We find that while a fully-hardware implementation results in average performance improvements of 8-46% for a range of TLB sizes, a hardware/software approach yields improvements of 4-32%. Overall, our work shows that TLB prefetchers exploiting inter-core correlations can effectively eliminate TLB misses.