An efficient 2D router architecture for extending the performance of inhomogeneous 3D NoC-based multi-core architectures

To meet the performance and scalability demands of the fast-paced technological growth towards exascale and Big-Data processing with the performance bottleneck of conventional metal based interconnects, alternative interconnect fabrics such as inhomogeneous three dimensional integrated Network-on-Chip (3D NoC) has emanated as a cost-effective solution for emerging multi-core design. However, these interconnects trade-off optimized performance for cost by restricting the number of area and power hungry 3D routers. Consequently, in this paper, we propose a low-latency adaptive router with a low-complexity single-cycle bypassing mechanism to alleviate the performance degradation due to the slow 2D routers in inhomogeneous 3D NoCs. By combining the low-complexity bypassing technique with adaptive routing, the proposed router is able to balance the traffic in the network to reduce the average packet latency under various traffic loads. Simulation shows that, the proposed router can reduce the average packet delay by an average of 45% in 3D NoCs

On Multicast in Asynchronous Networks-on-Chip: Techniques, Architectures, and FPGA Implementation

In this era of exascale computing, conventional synchronous design techniques are facing unprecedented challenges. The consumer electronics market is replete with many-core systems in the range of 16 cores to thousands of cores on chip, integrating multi-billion transistors. However, with this ever increasing complexity, the traditional design approaches are facing key issues such as increasing chip power, process variability, aging, thermal problems, and scalability. An alternative paradigm that has gained significant interest in the last decade is asynchronous design. Asynchronous designs have several potential advantages: they are naturally energy proportional, burning power only when active, do not require complex clock distribution, are robust to different forms of variability, and provide ease of composability for heterogeneous platforms. Networks-on-chip (NoCs) is an interconnect paradigm that has been introduced to deal with the ever-increasing system complexity. NoCs provide a distributed, scalable, and efficient interconnect solution for today’s many-core systems. Moreover, NoCs are a natural match with asynchronous design techniques, as they separate communication infrastructure and timing from the computational elements. To this end, globally-asynchronous locally-synchronous (GALS) systems that interconnect multiple processing cores, operating at different clock speeds, using an asynchronous NoC, have gained significant interest. While asynchronous NoCs have several advantages, they also face a key challenge of supporting new types of traffic patterns. Once such pattern is multicast communication, where a source sends packets to arbitrary number of destinations. Multicast is not only common in parallel computing, such as for cache coherency, but also for emerging areas such as neuromorphic computing. This important capability has been largely missing from asynchronous NoCs. This thesis introduces several efficient multicast solutions for these interconnects. In particular, techniques, and network architectures are introduced to support high-performance and low-power multicast. Two leading network topologies are the focus: a variant mesh-of-trees (MoT) and a 2D mesh. In addition, for a more realistic implementation and analysis, as well as significantly advancing the field of asynchronous NoCs, this thesis also targets synthesis of these NoCs on commercial FPGAs. While there has been significant advances in FPGA technologies, there has been only limited research on implementing asynchronous NoCs on FPGAs. To this end, a systematic computeraided design (CAD) methodology has been introduced to efficiently and safely map asynchronous NoCs on FPGAs. Overall, this thesis makes the following three contributions. The first contribution is a multicast solution for a variant MoT network topology. This topology consists of simple low-radix switches, and has been used in high-performance computing platforms. A novel local speculation technique is introduced, where a subset of the network’s switches are speculative that always broadcast every packet. These switches are very simple and have high performance. Speculative switches are surrounded by non-speculative ones that route packets based on their destinations and also throttle any redundant copies created by the former. This hybrid network architecture achieved significant performance and power benefits over other multicast approaches. The second contribution is a multicast solution for a 2D-mesh topology, which is more complex with higher-radix switches and also is more commonly used. A novel continuous-time replication strategy is introduced to optimize the critical multi-way forking operation of a multicast transmission. In this technique, a multicast packet is first stored in an input port of a switch, from where it is sent through distinct output ports towards different destinations concurrently, at each output’s own rate and in continuous time. This strategy is shown to have significant latency and energy benefits over an approach that performs multicast using multiple distinct serial unicasts to each destination. Finally, a systematic CAD methodology is introduced to synthesize asynchronous NoCs on commercial FPGAs. A two-fold goal is targeted: correctness and high performance. For ease of implementation, only existing FPGA synthesis tools are used. Moreover, since asynchronous NoCs involve special asynchronous components, a comprehensive guide is introduced to map these elements correctly and efficiently. Two asynchronous NoC switches are synthesized using the proposed approach on a leading Xilinx FPGA in 28 nm: one that only handles unicast, and the other that also supports multicast. Both showed significant energy benefits with some performance gains over a state-of-the-art synchronous switch

Towards the practical design of performance-aware resilient wireless NoC architectures

Recently, an improved surface wave-enabled communication fabric has been proposed to solve the reliability issues of emerging hybrid wired-wireless Network-on-Chip (WiNoC) architectures. Thus, providing a promising solution to the performance and scalability demands of the fast-paced technological growth towards exascale and Big-Data processing on future System-on-Chip (SoC) design. However, WiNoCs tradeoff optimized performance for cost by restricting the number of area and power hungry wireless nodes. Consequently, in this paper, we propose a low-latency adaptive router with a low-complexity single-cycle bypassing mechanism to alleviate the performance degradation due to the slow wired routers in such emerging hybrid NoCs. The proposed router is able to redistribute traffic in the network to alleviate average packet latency at both low and high traffic conditions. As a second contribution the paper presents an experimental evaluation of a practically implemented surface wave communication fabric. By reducing the latency between the wired nodes and wireless nodes the proposed router can improve performance efficiency in terms of average packet delay by an average of 50% in WiNoCs

Efficient bypass mechanisms for low latency networks on-chip

RESUMEN: La importancia de las redes en-chip en los procesadores multi-núcleo es cada vez mayor. Los routers con baipás son una solución eficiente para reducir la latencia de estas redes. Existen dos tipos de redes con baipás: single-hop y multi-hop. Las redes con baipás single-hop minimizan la latencia individual de cada router al asignar los recursos del router con antelación a la recepción de los paquetes. Las redes con baipás multi-hop, conocidas como SMART, permiten que los paquetes atraviesen múltiples routers en un único ciclo. La primera propuesta de esta tesis es Non-Empty Buffer Bypass (NEBB), un mecanismo que incrementa la utilización del baipás de tipo single-hop, eliminando la necesidad de usar canales virtuales. Para redes con baipás multi-hop propone SMART++ y S-SMART++. SMART++ elimina la necesidad de SMART de usar una gran cantidad de canales virtuales para aprovechar el ancho de banda de la red, permitiendo el diseño de configuraciones de bajo coste. S-SMART++ hace uso de la asignación de recursos de forma especulativa para preparar el baipás de tipo multi-hop. Este mecanismo reduce la latencia y su dependencia con la longitud máxima de los saltos de tipo multi-hop, aspecto clave para su viabilidad en diseños reales. La contribución final es un conjunto de herramientas de código abierto llamada Bypass Simulation Toolset (BST) compuesto por versiones extendidas de BookSim y OpenSMART, una API para integrar BookSim en otros simuladores y una serie de scripts para facilitar el diseño y evaluación de este tipo de redes.ABSTRACT: Networks on-Chip (NoCs) are becoming more important in many-core processors as the number of cores grows. Bypass routers are an efficient solution that skips pipeline stages. There are two types of bypass mechanisms: single-hop and multi-hop bypass. Single-hop bypass minimizes the router delay by skipping allocation stages in each hop. Multi-hop bypass, called SMART, minimizes the effective number of hops by traversing multiple routers in a single cycle. The first proposal of this dissertation is Non-Empty Buffer Bypass (NEBB) for single-hop bypass, which increases the bypass utilization without requiring VCs to match traditional bypass routers. It proposes SMART++ and S-SMART++ for multi-hop bypass. SMART++ removes the requirement of using multiple VCs of SMART to exploit the bandwidth of the network, enabling low-cost configurations. S-SMART++ relies on speculative allocation to set up multi-hop bypass paths. Thus, it reduces latency and its dependency with the maximum length of multi-hops, relaxing the requirements to integrate multi-hop bypass in real designs. The final contribution is an open-source set of tools to simulate bypass NoCs called Bypass Simulation Toolset (BST) conformed by extended versions of BookSim and OpenSMART, an API to integrate BookSim in other simulators, and scripts to simplify the designing and evaluation of such NoCs.This work was supported by the Spanish Ministry of Science, Innovation and Universities, FPI grant BES-2017-079971, and contracts TIN2010-21291-C02-02, TIN2013- 46957-C2-2-P, TIN2015-65316-P, TIN2016-76635-C2-2-R (AEI/FEDER, UE) and TIC PID2019-105660RB-C22; the European HiPEAC Network of Excellence; the European Community's Seventh Framework Programme (FP7/2007-2013), under the Mont-Blanc 1 and 2 projects (grant agreements n 288777 and 610402); the European Union's Horizon 2020 research and innovation programme under the Mont-Blanc 3 project (grant agreement nº 671697). Bluespec Inc. provided access to Bluespec tools

Network-on-Chip

Addresses the Challenges Associated with System-on-Chip Integration Network-on-Chip: The Next Generation of System-on-Chip Integration examines the current issues restricting chip-on-chip communication efficiency, and explores Network-on-chip (NoC), a promising alternative that equips designers with the capability to produce a scalable, reusable, and high-performance communication backbone by allowing for the integration of a large number of cores on a single system-on-chip (SoC). This book provides a basic overview of topics associated with NoC-based design: communication infrastructure design, communication methodology, evaluation framework, and mapping of applications onto NoC. It details the design and evaluation of different proposed NoC structures, low-power techniques, signal integrity and reliability issues, application mapping, testing, and future trends. Utilizing examples of chips that have been implemented in industry and academia, this text presents the full architectural design of components verified through implementation in industrial CAD tools. It describes NoC research and developments, incorporates theoretical proofs strengthening the analysis procedures, and includes algorithms used in NoC design and synthesis. In addition, it considers other upcoming NoC issues, such as low-power NoC design, signal integrity issues, NoC testing, reconfiguration, synthesis, and 3-D NoC design. This text comprises 12 chapters and covers: The evolution of NoC from SoC—its research and developmental challenges NoC protocols, elaborating flow control, available network topologies, routing mechanisms, fault tolerance, quality-of-service support, and the design of network interfaces The router design strategies followed in NoCs The evaluation mechanism of NoC architectures The application mapping strategies followed in NoCs Low-power design techniques specifically followed in NoCs The signal integrity and reliability issues of NoC The details of NoC testing strategies reported so far The problem of synthesizing application-specific NoCs Reconfigurable NoC design issues Direction of future research and development in the field of NoC Network-on-Chip: The Next Generation of System-on-Chip Integration covers the basic topics, technology, and future trends relevant to NoC-based design, and can be used by engineers, students, and researchers and other industry professionals interested in computer architecture, embedded systems, and parallel/distributed systems

Run-time management of many-core SoCs: A communication-centric approach

The single core performance hit the power and complexity limits in the beginning of this century, moving the industry towards the design of multi- and many-core system-on-chips (SoCs). The on-chip communication between the cores plays a criticalrole in the performance of these SoCs, with power dissipation, communication latency, scalability to many cores, and reliability against the transistor failures as the main design challenges. Accordingly, we dedicate this thesis to the communicationcentered management of the many-core SoCs, with the goal to advance the state-ofthe-art in addressing these challenges. To this end, we contribute to on-chip communication of many-core SoCs in three main directions. First, we start with a synthesizable SoC with full system simulation. We demonstrate the importance of the networking overhead in a practical system, and propose our sophisticated network interface (NI) that offloads the work from SW to HW. Our results show around 5x and up to 50x higher network performance, compared to previous works. As the second direction of this thesis, we study the significance of run-time application mapping. We demonstrate that contiguous application mapping not only improves the network latency (by 23%) and power dissipation (by 50%), but also improves the system throughput (by 3%) and quality-of-service (QoS) of soft real-time applications (up to 100x less deadline misses). Also our hierarchical run-time application mapping provides 99.41% successful mapping when up to 8 links are broken. As the final direction of the thesis, we propose a fault-tolerant routing algorithm, the maze-routing. It is the first-in-class algorithm that provides guaranteed delivery, a fully-distributed solution, low area overhead (by 16x), and instantaneous reconfiguration (vs. 40K cycles down time of previous works), all at the same time. Besides the individual goals of each contribution, when applicable, we ensure that our solutions scale to extreme network sizes like 12x12 and 16x16. This thesis concludes that the communication overhead and its optimization play a significant role in the performance of many-core SoC

Architectural Support for Efficient Communication in Future Microprocessors

Traditionally, the microprocessor design has focused on the computational aspects of the problem at hand. However, as the number of components on a single chip continues to increase, the design of communication architecture has become a crucial and dominating factor in defining performance models of the overall system. On-chip networks, also known as Networks-on-Chip (NoC), emerged recently as a promising architecture to coordinate chip-wide communication. Although there are numerous interconnection network studies in an inter-chip environment, an intra-chip network design poses a number of substantial challenges to this well-established interconnection network field. This research investigates designs and applications of on-chip interconnection network in next-generation microprocessors for optimizing performance, power consumption, and area cost. First, we present domain-specific NoC designs targeted to large-scale and wire-delay dominated L2 cache systems. The domain-specifically designed interconnect shows 38% performance improvement and uses only 12% of the mesh-based interconnect. Then, we present a methodology of communication characterization in parallel programs and application of characterization results to long-channel reconfiguration. Reconfigured long channels suited to communication patterns enhance the latency of the mesh network by 16% and 14% in 16-core and 64-core systems, respectively. Finally, we discuss an adaptive data compression technique that builds a network-wide frequent value pattern map and reduces the packet size. In two examined multi-core systems, cache traffic has 69% compressibility and shows high value sharing among flows. Compression-enabled NoC improves the latency by up to 63% and saves energy consumption by up to 12%

Exploration and Design of Power-Efficient Networked Many-Core Systems

Multiprocessing is a promising solution to meet the requirements of near future applications. To get full benefit from parallel processing, a manycore system needs efficient, on-chip communication architecture. Networkon- Chip (NoC) is a general purpose communication concept that offers highthroughput, reduced power consumption, and keeps complexity in check by a regular composition of basic building blocks. This thesis presents power efficient communication approaches for networked many-core systems. We address a range of issues being important for designing power-efficient manycore systems at two different levels: the network-level and the router-level. From the network-level point of view, exploiting state-of-the-art concepts such as Globally Asynchronous Locally Synchronous (GALS), Voltage/ Frequency Island (VFI), and 3D Networks-on-Chip approaches may be a solution to the excessive power consumption demanded by today’s and future many-core systems. To this end, a low-cost 3D NoC architecture, based on high-speed GALS-based vertical channels, is proposed to mitigate high peak temperatures, power densities, and area footprints of vertical interconnects in 3D ICs. To further exploit the beneficial feature of a negligible inter-layer distance of 3D ICs, we propose a novel hybridization scheme for inter-layer communication. In addition, an efficient adaptive routing algorithm is presented which enables congestion-aware and reliable communication for the hybridized NoC architecture. An integrated monitoring and management platform on top of this architecture is also developed in order to implement more scalable power optimization techniques. From the router-level perspective, four design styles for implementing power-efficient reconfigurable interfaces in VFI-based NoC systems are proposed. To enhance the utilization of virtual channel buffers and to manage their power consumption, a partial virtual channel sharing method for NoC routers is devised and implemented. Extensive experiments with synthetic and real benchmarks show significant power savings and mitigated hotspots with similar performance compared to latest NoC architectures. The thesis concludes that careful codesigned elements from different network levels enable considerable power savings for many-core systems.Siirretty Doriast

Design Space Exploration for MPSoC Architectures

Multiprocessor system-on-chip (MPSoC) designs utilize the available technology and communication architectures to meet the requirements of the upcoming applications. In MPSoC, the communication platform is both the key enabler, as well as the key differentiator for realizing efficient MPSoCs. It provides product differentiation to meet a diverse, multi-dimensional set of design constraints, including performance, power, energy, reconfigurability, scalability, cost, reliability and time-to-market. The communication resources of a single interconnection platform cannot be fully utilized by all kind of applications, such as the availability of higher communication bandwidth for computation but not data intensive applications is often unfeasible in the practical implementation. This thesis aims to perform the architecture-level design space exploration towards efficient and scalable resource utilization for MPSoC communication architecture. In order to meet the performance requirements within the design constraints, careful selection of MPSoC communication platform, resource aware partitioning and mapping of the application play important role. To enhance the utilization of communication resources, variety of techniques such as resource sharing, multicast to avoid re-transmission of identical data, and adaptive routing can be used. For implementation, these techniques should be customized according to the platform architecture. To address the resource utilization of MPSoC communication platforms, variety of architectures with different design parameters and performance levels, namely Segmented bus (SegBus), Network-on-Chip (NoC) and Three-Dimensional NoC (3D-NoC), are selected. Average packet latency and power consumption are the evaluation parameters for the proposed techniques. In conventional computing architectures, fault on a component makes the connected fault-free components inoperative. Resource sharing approach can utilize the fault-free components to retain the system performance by reducing the impact of faults. Design space exploration also guides to narrow down the selection of MPSoC architecture, which can meet the performance requirements with design constraints.Siirretty Doriast