ControlPULP: A RISC-V Power Controller for HPC Processors with Parallel Control-Law Computation Acceleration

High-Performance Computing (HPC) processors are nowadays integrated Cyber-Physical Systems requiring complex and high-performance closed-loop control strategies for efficient power and thermal management. To satisfy high-bandwidth, real-time multi-input multi-output (MIMO) optimal power control requirements, high-end processors integrate on-die Power Controller Systems (PCS). Traditional PCS is based on a simple microcontroller core supported by dedicated interface logic and sequencers. More scalable and flexible PCS architectures are required to support advanced MIMO control algorithms required for managing the ever-increasing number of cores, power states, and process, voltage, temperature (PVT) variability. In this paper, we present ControlPULP, a complete, open-source HW/SW RISC-V parallel PCS platform consisting of a single-core microcontroller coupled with a scalable multi-core cluster system with a specialized DMA engine and a fast multi-core interrupt controller for parallel acceleration of real-time power management policies. ControlPULP relies on a real-time OS (FreeRTOS) to schedule a Power Control Firmware (PCF) software layer. We evaluate ControlPULP design choices in a cycle-accurate, event-based simulation environment and show the benefits of the proposed multi-core acceleration solution. We demonstrate ControlPULP in a PCS use-case targeting a next-generation 72-cores HPC processor. We show that the multi-core cluster accelerates the PCF achieving 4.9x speedup with respect to single-core execution.