Distributed Control and Coordination for Massively Integrated Multicore Platforms

持续的技术扩展允许在同一芯片上集成数十或数百个处理核心；这代表了多核计算范式，这使得在单个芯片上并发运行多个异构应用程序成为可能。在这种多处理器系统中，单个处理节点可以通过片上网络（noc）进行通信和协调。因此，一个主要的挑战是确定以严格的方式设计和优化这种片上网络的数学技术。最近的多核平台（如英特尔单芯片云计算机）受益于支持动态电压和频率缩放（DVFS）的多电压和频率岛（VFI）设计风格。在这样的系统中，每个岛的电压和频率可以独立于所有其他岛进行设置，并在运行时根据应用特性的时间变化进行调整。工作负载的时空变化会导致不同的片上功率和热梯度，这也引起了对寿命可靠性的主要关注。因此，片上电源和热管理已成为多核设计流程中每一步的关键组成部分，从物理设计一直到微架构和系统级设计。从这些总体思想出发，本项目解决了在基于vfi的多核系统中设计有效且高度可扩展的电源和热管理控制算法的基本问题。与该领域的许多现有工作不同，本研究的重点是真正可扩展的系统级设计方法，该方法可以利用由数百或数千个内核组成的系统在电路级（例如，电压，频率）上的现有旋钮。同时，所提出的控制技术可用于调节其他片上共享资源，如网络带宽或片外带宽。这种新的设计方法使开发各种节能多核应用成为可能，从游戏和娱乐平台到通信系统、数据中心和车辆交通管理。更广泛地说，这个项目的结果通过提高对设计和控制复杂系统所需的网络概念的理解水平，对其他研究团体产生了重大影响。

Continuous technology scaling allows tens or hundreds of processing cores integrated on the same chip; this represents the multicore computing paradigm which makes it possible to run multiple heterogeneous applications concurrently on a single chip. In such multiprocessor systems, individual processing nodes can communicate and coordinate via networks-on-chip (NoCs). Therefore, a major challenge is to determine the mathematical techniques for designing and optimizing such on-chip networks in a rigorous manner.Recent multicore platforms (such as Intel Single Chip Cloud Computer) benefit from the multiple voltage and frequency island (VFI) design style with support for dynamic voltage and frequency scaling (DVFS). In such systems, the voltage and frequency of each island can be set independently of all other islands and adapt at run-time in response to temporal variations in application characteristics. Spatio-temporal workload variations result in various on-chip power and thermal gradients, which also raise major concerns for lifetime reliability. On-chip power and thermal management has therefore become a critical component of every step in the multicore design flow, from physical design all the way up to micro-architecture and system-level design.Starting from these overarching ideas, this project addresses the fundamental issue of designing effective and highly scalable control algorithms for power and thermal management in VFI-based multicore systems. Unlike much of the existing work in this area, the focus of this research is on truly scalable system-level design methodologies that can take advantage of the existing knobs at circuit-level (e.g., voltage, frequency) for systems comprised of hundreds or thousands of cores. At the same time, the proposed control techniques may be useful for regulating other on-chip shared resources such as network bandwidth or off-chip bandwidth.This new design methodology enables the development of a wide variety of energy-efficient multicore applications ranging from gaming and entertainment platforms, to communication systems, data centers, and vehicular traffic management. More broadly, the results of this project impact significantly other research communities by improving the level of understanding of networking concepts needed to design and control complex systems.