SRAM- and STT-RAM-based hybrid, shared last-level cache for on-chip CPU–GPU heterogeneous architectures

Abstract

Shared last-level cache (LLC) in on-chip CPU–GPU heterogeneous architectures is critical to the overall system performance, since CPU and GPU applications usually show completely different characteristics on cache accesses. Therefore, when co-running with CPU applications, GPU ones can easily occupy the majority of the LLC, making CPU applications starve severely. This imposes significant challenges to the design and management of the shared LLC in CPU–GPU heterogeneous architectures. To improve the overall system performance, we consider integrating conventional SRAM and a new memory technology (i.e., STT-RAM) to enlarge the shared LLC. Furthermore, we propose comprehensive management policies to reduce the contention between CPU and GPU units. Experimental results show that, compared with the conventional SRAM-only LLC design, our proposal improves the performance of CPU workloads by 17% while not hurting GPU ones and reduces the LLC energy consumption by 30% on average.