Tuning the ISA for increased heterogeneous computation in MPSoCs

• Published in: 2020 Design, Automation & Test in Europe Conference & Exhibition (DATE) pp. 1722 - 1727
• Main Authors: Becker, Pedro H. E., Souza, Jeckson D., Beck, Antonio C. S.
• Format: Conference Proceeding
• Language: English
• Published: EDAA 01.03.2020
• Subjects: Computer architecture; Cryptography; Energy consumption; Hardware; Heterogeneous Systems; Instruction sets; Microarchitecture; MPSoC Design; Partial-ISA; Task analysis
• ISSN: 1558-1101
• DOI: 10.23919/DATE48585.2020.9116547

Heterogeneous MPSoCs are crucial to meeting energy efficiency and performance, given their combination of cores and accelerators. In this work, we propose a novel technique for MPSoCs design, increasing their specialization and task-parallelism within a given area and power budget. By removing the microarchitectural support of costly ISA extensions (e.g., FP, SIMD, crypto) from a few cores (transforming them into PartialISA Cores), we make room to add extra (full and simpler) inorder cores and hardware accelerators. While applications must migrate from Partial-ISA cores when they need the removed ISA support, they also execute at lower power consumption during their ISA-extension-free phases, since partial cores have much simpler datapaths compared to their full-ISA counterparts. On top of it, the additional cores and accelerators increase task-level parallelism and make the MPSoC more suitable for application-specific scenarios. We show the effectiveness of our approach by composing different MPSoCs in distinct execution scenarios, using the FP instructions and RISC-V ISA as a case study. To support our system, we also propose two scheduling policies, performance- and energy-oriented, to coordinate the execution of this novel design. For the former policy, we achieve 2.8× speedup for a neural network road sign detection, 1.53x speedup for a video-streaming app, and 1.2x speedup for a taskparallel scenario, consuming 68%, 75%, and 33% less energy, respectively. For the energy-oriented policy, partial-ISA reduces energy consumption by 29% over a highly efficient baseline, with increased performance.