HSM: A Hybrid Slowdown Model for Multitasking GPUs
Session: SIMT--So many instructions, multiple tricks!
Authors: Xia Zhao (Ghent University); Magnus Jahre (Norwegian University of Science and Technology); Lieven Eeckhout (Ghent University)
Graphics Processing Units (GPUs) are increasingly widely used in the cloud to accelerate compute-heavy tasks. However, GPU-compute applications stress the GPU architecture in different ways -- leading to suboptimal resource utilization when a single GPU is used to run a single application. One solution is to use the GPU in a multitasking fashion to improve utilization. Unfortunately, multitasking leads to destructive interference between co-running applications which causes fairness issues and Quality-of-Service (QoS) violations. We propose the Hybrid Slowdown Model (HSM) to dynamically and accurately predict application slowdown due to interference. HSM overcomes the low accuracy of prior white-box models, and training and implementation overheads of pure black-box models, with a hybrid approach. More specifically, the white-box component of HSM builds upon the fundamental insight that effective bandwidth utilization is proportional to DRAM row buffer hit rate, and the black-box component of HSM uses linear regression to relate row buffer hit rate to performance. HSM accurately predicts application slowdown with an average error of 6.8%, a significant improvement over the current state-of-the-art. In addition, we use HSM to guide various resource management schemes in multitasking GPUs: HSM-Fair significantly improves fairness (by 1.59x on average) compared to even partitioning, whereas HSM-QoS improves system throughput (by 18.9% on average) compared to proportional SM partitioning while maintaining the QoS target for the high-priority application in challenging mixed memory/compute-bound multi-program workloads.