International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

The drive for higher performance and energy efficiency in data-centers has influenced trends toward increased power and cooling requirements in the facilities. Since enterprise servers rarely operate at their peak capacity, efficient power capping is deemed as a critical component of modern enterprise computing environments. In this paper we propose a new power measurement and power limiting architecture for main memory. Specifically, we describe a new approach for measuring memory power and demonstrate its applicability to a novel power limiting algorithm. We implement and evaluate our approach in the modern servers and show that we achieve up to 40% lower performance impact when compared to the state-of-art baseline across the power limiting range.

RAPL: memory power estimation and capping

The ability to cap peak power consumption is a desirable feature in modern data centers for energy budgeting, cost management, and efficient power delivery. Dynamic voltage and frequency scaling (DVFS) is a traditional control knob in the tradeoff between server power and performance. Multi-core processors and the parallel applications that take advantage of them introduce new possibilities for control, wherein workload threads are packed onto a variable number of cores and idle cores enter low-power sleep states. This paper proposes Pack & Cap, a control technique designed to make optimal DVFS and thread packing control decisions in order to maximize performance within a power budget. In order to capture the workload dependence of the performance-power Pareto frontier, a multinomial logistic regression (MLR) classifier is built using a large volume of performance counter, temperature, and power characterization data. When queried during runtime, the classifier is capable of accurately selecting the optimal operating point. We implement and validate this method on a real quad-core system running the PARSEC parallel benchmark suite. When varying the power budget during runtime, Pack & Cap meets power constraints 82% of the time even in the absence of a power measuring device. The addition of thread packing to DVFS as a control knob increases the range of feasible power constraints by an average of 21% when compared to DVFS alone and reduces workload energy consumption by an average of 51.6% compared to existing control techniques that achieve the same power range.

http://www.bu.edu/dbin/ece/people/acoskun/cochran_MICRO11.pdf

Pack & Cap: adaptive DVFS and thread packing under power caps

Dynamic Voltage Frequency Scaling (DVFS) has been the tool of choice for balancing power and performance in high-performance computing (HPC). With the introduction of Intel's Sandy Bridge family of processors, researchers now have a far more attractive option: user-specified, dynamic, hardware-enforced processor power bounds. In this paper we provide a first look at this technology in the HPC environment and detail both the opportunities and potential pitfalls of using this technique to control processor power. As part of this evaluation we measure power and performance for single-processor instances of several of the NAS Parallel Benchmarks. Additionally, we focus on the behavior of a single benchmark, MG, under several different power bounds. We quantify the well-known manufacturing variation in processor power efficiency and show that, in the absence of a power bound, this variation has no correlation to performance. We then show that execution under a power bound translates this variation in efficiency into variation in performance.

/pdf/beyond-dvfs-a-first-look-at-performance-under-a-hardware-28e8xcwxho.pdf

Beyond DVFS: A First Look at Performance under a Hardware-Enforced Power Bound

Heterogeneous multicore systems -- comprised of multiple cores with varying capabilities, performance, and energy characteristics -- have emerged as a promising approach to increasing energy efficiency. Such systems reduce energy consumption by identifying phase changes in an application and migrating execution to the most efficient core that meets its current performance requirements. However, due to the overhead of switching between cores, migration opportunities are limited to coarse-grained phases (hundreds of millions of instructions), reducing the potential to exploit energy efficient cores. We propose Composite Cores, an architecture that reduces switching overheads by bringing the notion of heterogeneity within a single core. The proposed architecture pairs big and little compute µEngines that together can achieve high performance and energy efficiency. By sharing much of the architectural state between the µEngines, the switching overhead can be reduced to near zero, enabling fine-grained switching and increasing the opportunities to utilize the little µEngine without sacrificing performance. An intelligent controller switches between the µEngines to maximize energy efficiency while constraining performance loss to a configurable bound. We evaluate Composite Cores using cycle accurate micro architectural simulations and a detailed power model. Results show that, on average, the controller is able to map 25% of the execution to the little µEngine, achieving an 18% energy savings while limiting performance loss to 5%.

/pdf/composite-cores-pushing-heterogeneity-into-a-core-xjgndriqcu.pdf

Composite Cores: Pushing Heterogeneity Into a Core

This paper describes an architecture for a dynamically heterogeneous processor architecture leveraging 3D stacking technology. Unlike prior work in the 2D plane, the extra dimension makes it possible to share resources at a fine granularity between vertically stacked cores. As a result, each core can grow or shrink resources, as needed by the code running on the core. This architecture, therefore, enables runtime customization of cores at a fine granularity and enables efficient execution at both high and low levels of thread parallelism. This architecture achieves performance gains from 9–41%, depending on the number of executing threads, and gains significant advantage in energy efficiency of up to 43%.

/pdf/dynamically-heterogeneous-cores-through-3d-resource-pooling-25wk23lrvn.pdf

Dynamically heterogeneous cores through 3D resource pooling

The increasing power dissipation of current processors and processor cores constrains design options, increases packaging and cooling costs, increases power delivery costs, and decreases reliability. Much research has been focused on decreasing average power dissipation, which most directly addresses cooling costs and reliability. However, much less has been done to decrease peak power, which most directly impacts the processor design, packaging, and power delivery. This research proposes a new architecture which provides a significant decrease in peak power with limited performance loss. It does this through the use of a highly adaptive processor. Many components of the processor can be configured at different levels, but because they are centrally controlled, the architecture can guarantee that they are never all configured maximally at the same time. This paper describes this adaptive processor and explores mechanisms for transitioning between allowed configurations to maximize performance within a peak power constraint. Such an architecture can cut peak power by 25% with less than 5% performance loss; among other advantages, this frees 5.3% of total core area used for decoupling capacitors.

/pdf/reducing-peak-power-with-a-table-driven-adaptive-processor-3w7nt8bw8u.pdf

Reducing peak power with a table-driven adaptive processor core

An on-chip sensor measures dynamic power supply noise, such as voltage droop, on a semiconductor chip. In-situ logic is employed, which is sensitive to noise present on the power supply of functional logic of the chip. Exemplary functional logic includes a microprocessor, adder, and/or other functional logic of the chip. The in-situ logic performs some operation, and the amount of time required for performing that operation (i.e., the operational delay) is sensitive to noise present on the power supply. Thus, by evaluating the operational delay of the in-situ logic, the amount of noise present on the power supply can be measured.

On-chip sensor for measuring dynamic power supply noise of the semiconductor chip

Reliable design of power distribution network for stacked integrated circuits introduces new challenges i.e., substrate coupling among through silicon vias (TSVs) and tiers grid in addition to reliability issues such as electromigration and thermo-mechanical stress, compared to conventional System on Chip (SoC). In this paper a comprehensive modeling of the TSV and stacked power grid with frequency dependent parasitic is proposed. The analytical model considers the impact of the substrate coupling between the TSVs and layers grid. A frequency domain based analysis flow is introduced to incorporate frequency dependent parasitics. The design of a reliable power distribution network is formulated as an optimization problem to minimize power noise under reliability and electro-migration constraints. Experimental results demonstrate the efficacy of the problem formulation and solution technique.

/pdf/3d-stacked-power-distribution-considering-substrate-coupling-13elg3dfqn.pdf

3D stacked power distribution considering substrate coupling

This work proposes reliability aware through silicon via (TSV) planning for the 3D stacked silicon integrated circuits (ICs). The 3D power distribution network is modeled and extracted in frequency domain which includes the impact of skin effect. The worst case power noise of the 3D power delivery networks (PDN) with local TSV failures resulting from fabrication process or circuit operation is identified in both frequency and time domain. From the experimental results, it is observed that a single TSV failure could increase the maximum voltage variation up to 70% which should be considered in nanoscale ICs. The parameters of the 3D PDN are designed such that the power distribution is reliable under local TSV failures. The spatial distribution of the power noise, reliability and block out area is analyzed to enhance the reliability of the 3D PDN under local TSV failure.

Amirali Shayan

Papers

Dynamically heterogeneous cores through 3D resource pooling

Reducing peak power with a table-driven adaptive processor core

On-chip sensor for measuring dynamic power supply noise of the semiconductor chip

3D stacked power distribution considering substrate coupling

Reliability aware through silicon via planning for 3D stacked ICs