Leveraging Processor-diversity For Improved Performance In Heterogeneous-ISA Systems

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Virginia Tech

The purpose of this thesis is to investigate the effectiveness of executing High Performance Computing (HPC) workloads on multiprocessors with heterogeneous Instruction Set Architecture (ISA) cores. ISA-heterogeneity in processor designs provides a unique dimension for researchers to explore performance benefits through diversity in design choices. Additionally, each application has a natural preference to one processor in a selected group of processors (we defined this term as processor-preference), and processor-preference is highly affected by processor design choices. Thus, a system with heterogeneous-ISA cores offers an intriguing design perspective, packing heterogeneous-ISA cores in the same processor or system that compensate each other in dynamic workload scenarios. This thesis considers dynamic migrating applications with different processor-preferences across ISA-different cores to exploit the potential of this idea. With SIMD instructions getting more attention from chip designers, this thesis also presents the necessary modifications for a general compiler/run-time infrastructure to transform the dynamic program state of SIMD regions at run-time from one ISA format to another for cross-ISA migration and execution. Lastly, this thesis presents a processor-preference-aware scheduling policy that makes dynamic cross-ISA migration decisions that improve overall system throughput compared to homogeneous-ISA systems. This thesis prototypes a heterogeneous-ISA system using an Intel Xeon Gold 5118 x86-64 server and a Cavium ThunderX ARMv8 server and evaluates the effectiveness of our infrastructure and scheduling policy. Our results reveal that heterogeneous-ISA systems that are processor-preference-aware and with cross-ISA execution migration capability can yield throughput gains up to 36% compared to traditional homogeneous ISA systems.

System Software, Heterogeneous Architectures, SIMD, Scheduling, ISA