FlexWatts: A Power- and Workload-Aware Hybrid Power Delivery Network for Energy-Efficient Microprocessors
- 1 October 2020
- conference paper
- conference paper
- Published by Institute of Electrical and Electronics Engineers (IEEE) in 2020 53rd Annual IEEE/ACM International Symposium on Microarchitecture (MICRO)
- p. 1051-1066
- https://doi.org/10.1109/micro50266.2020.00088
Abstract
Modern client processors typically use one of three commonly-used power delivery network (PDN) architectures: 1) motherboard voltage regulators (MBVR), 2) integrated voltage regulators (IVR), and 3) low dropout voltage regulators (LDO). We observe that the energy-efficiency of each of these PDNs varies with the processor power (e.g, thermal design power (TDP) and dynamic power-state) and workload characteristics (e.g., work-load type and computational intensity). This leads to energy-inefficiency and performance loss, as modern client processors operate across a wide spectrum of power consumption and execute a wide variety of workloads.To address this inefficiency, we propose FlexWatts, a hybrid adaptive PDN for modern client processors whose goal is to provide high energy-efficiency across the processor’s wide range of power consumption and workloads. FlexWatts provides high energy-efficiency by intelligently and dynamically allocating PDNs to processor domains depending on the processor’s power consumption and workload. FlexWatts is based on three key ideas. First, FlexWatts combines IVRs and LDOs in a novel way to share multiple on-chip and off-chip resources and thus reduce cost, as well as board and die area overheads. This hybrid PDN is allocated for processor domains with a wide power consumption range (e.g., CPU cores and graphics engines) and it dynamically switches between two modes: IVR-Mode and LDO-Mode, depending on the power consumption. Second, for all other processor domains (that have a low and narrow power range, e.g., the IO domain), FlexWatts statically allocates off-chip VRs, which have high energy-efficiency for low and narrow power ranges. Third, FlexWatts introduces a novel prediction algorithm that automatically switches the hybrid PDN to the mode (IVR-Mode or LDO-Mode) that is the most beneficial based on processor power consumption and workload characteristics.To evaluate the tradeoffs of PDNs, we develop and open-source PDNspot, the first validated architectural PDN model that enables quantitative analysis of PDN metrics. Using PDNspot, we evaluate FlexWatts on a wide variety of SPEC CPU2006, graphics (3DMark06), and battery life (e.g., video playback) workloads against IVR, the state-of-the-art PDN in modern client processors. For a 4 W thermal design power (TDP) processor, FlexWatts improves the average performance of the SPEC CPU2006 and 3DMark06 workloads by 22% and 25%, respectively. For battery life workloads, FlexWatts reduces the average power consumption of video playback by 11% across all tested TDPs (4W–50W). FlexWatts has comparable cost and area overhead to IVR. We conclude that FlexWatts provides high energy-efficiency across a modern client processor’s wide range of power consumption and wide variety of workloads, with minimal overhead.Keywords
This publication has 69 references indexed in Scilit:
- Broadwell: A family of IA 14nm processorsPublished by Institute of Electrical and Electronics Engineers (IEEE) ,2015
- CPU Power ManagementPublished by Springer Science and Business Media LLC ,2015
- Intel Atom C2000 Processor Family: Power-Efficient Datacenter ProcessingIEEE Micro, 2015
- Compiler-Directed Power Management for SuperscalarsACM Transactions on Architecture and Code Optimization, 2015
- Wake-up latencies for processor idle states on current x86 processorsComputer Science - Research and Development, 2014
- Haswell: The Fourth-Generation Intel Core ProcessorIEEE Micro, 2014
- Quantifying the relationship between the power delivery network and architectural policies in a 3D-stacked memory devicePublished by Association for Computing Machinery (ACM) ,2013
- Evaluation of CPU frequency transition latencyComputer Science - Research and Development, 2013
- VRSyncACM SIGARCH Computer Architecture News, 2012
- Generic Bill-of-Materials-and-Operations for High-Variety Production ManagementConcurrent Engineering, 2000