DUB: dynamic underclocking and bypassing in nocs for heterogeneous GPU workloads

Srikant Bharadwaj, Shomit Das, Yasuko Eckert, Mark Oskin, Tushar Krishna

Abstract: The performance of graphics processing units (GPU) workloads can be sensitive to the various clock domains which are dynamically tunable in modern GPUs. In this work, we observe that GPU application performance is sensitive towards NoC clock frequencies and the sensitivity varies during the execution of GPU kernels. We note that this heterogeneity is not adapted well by traditional dynamic voltage frequency scaling (DVFS) techniques. To that end, we introduce DUB, <u>D</u>ynamic <u>U</u>nderclocking and <u>B</u>ypassing technique, for such heterogeneous GPU workloads. We enable bypassing re-timer flops and routers while underclocking the NoC frequency thus enabling high power savings at minimal performance loss. Compared to baseline we observe a 26% improvement in power savings with only 3% degradation in performance beating oracular DVFS techniques.