Resource Optimized Scheduling For Enhanced Power Efficiency And Throughput On Chip Multi Processor Platforms

The parallel nature of process execution on Chip Multi-Processors (CMPs) has boosted levels of application performance far beyond the capabilities of erstwhile single-core designs. Generally, CMPs offer improved performance by integrating multiple simpler cores onto a single die that share certain computing resources among them such as last-level caches, data buses, and main memory. This ensures architectural simplicity while also boosting performance for multi-threaded applications. However, a major trade-off associated with this approach is that concurrently executing applications incur performance degradation if their collective resource requirements exceed the total amount of resources available to the system. If dynamic resource allocation is not carefully considered, the potential performance gain from having multiple cores may be outweighed by the losses due to contention for allocation of shared resources. Additionally, CMPs with inbuilt dynamic voltage-frequency scaling (DVFS) mechanisms may try to compensate for the performance bottleneck by scaling to higher clock frequencies. For performance degradation due to shared-resource contention, this does not necessarily improve performance but does ensure a significant penalty on power consumption due to the quadratic relation of electrical power and voltage (P_dynamic ∝ V^2 * f).This dissertation presents novel methodologies for balancing the competing requirements of high performance, fairness of execution, and enforcement of priority, while also ensuring overall power efficiency of CMPs. Specifically, we (1) Analyze the problem of resource interference during concurrent process execution and propose two fine-grained scheduling methodologies for improving overall performance and fairness, (2) Develop an approach for enforcement of priority (i.e., minimum performance) for specific processes while avoiding resource starvation for others, and (3) Present a machine-learning approach for maximizing the power efficiency (performance-per-Watt) of CMPs through estimation of a workload\u27s performance and power consumption limits at different clock frequencies.As modern computing workloads become increasingly dynamic, and computers themselves become increasingly ubiquitous, the problem of finding the ideal balance between performance and power consumption of CMPs is of particular relevance today, especially given the unprecedented proliferation of embedded devices for use in Internet-of-Things, edge computing, smart wearables, and even exotic experiments such as space probes comprised entirely of a CMP, sensors, and an antenna ( space chips ). Additionally, reducing power consumption while maintaining constant performance can contribute to addressing the growing problem of dark silicon

Towards Energy-Efficient Heterogeneous Multicore Architectures for Edge Computing

International audienceIn recent years, the edge computing paradigm has been attracting much attention in the Internet-of-Things domain. It aims to push the frontier of computing applications, data, and services away from the usually centralized cloud servers, to the boundary of the network. The benefits of this paradigm shift include better reactivity and reliability, reduced data transfer costs towards the centralized cloud servers, and enhanced confidentiality. The design of energy-efficient edge compute nodes requires, among others, low power cores such as microprocessors. Heterogeneous architectures are key solutions to address the crucial energy-efficiency demand in modern systems. They combine various processors providing attractive power and performance trade-offs. Unfortunately, no standard heterogeneous microcontroller-based architecture exists for edge computing. This paper deals with the aforementioned issue by exploring typical low power architectures for edge computing. Various heterogeneous multicore designs are developed and prototyped on FPGA for unbiased evaluation. These designs rely on cost-effective and inherently ultra-low power cores commercialized by Cortus SA, a world-leading semiconductor IP company in the embedded ultra-low-power microcontroller domain. Some microarchitecture-level design considerations, e.g. floating point and out-of-order computing capabilities, are taken into account for exploring candidate solutions. In addition, a tailored and flexible multi-task programming model is defined for the proposed architecture paradigm. We analyze the behavior of various application programs on available core configurations. This provides valuable insights on the best architecture setups that match program characteristics, so as to enable increased energy-efficiency. Our experiments on multi-benchmark programs show that on average 22% energy gain can be achieved (up to 45%) compared to a reference system design, i.e., a system with the same execution architecture, but agnostic of the task management insights gained from the comprehensive evaluation carried out in this work