Bandwidth-Aware Loop Tiling for DMA-Supported Scratchpad Memory
Ming-Chuan Wu, Ying Liu, Huimin Cui, Qingfu Wei, Quanfeng Li, Limin Li, Fang Lv, Jingling Xue, Xiaobing Feng · 2020
Scratchpad Memory (SPM) is widely used in emerging domain-specific architectures and accelerators for improving energy efficiency and time predictability. Typically, SPM-based architectures use DMA for fetching data from off-chip memory and global load instructions for loading fine-grained data directly into registers. For such architectures, neither capacity-only nor bandwidth-only loop tiling can efficiently use the bandwidth and SPM. This paper introduces a bandwidth-aware loop tiling approach that enables a tradeoff between SPM space utilization and bandwidth utilization to be made, by leveraging a runtime tiling framework and a cross-host-kernel IPA. Experimental results demonstrate that our approach can achieve the performance improvement of up to 4x, with a geometric average of 26%.