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1. A Versatile and Flexible Chiplet-based System Design for Heterogeneous Manycore Architectures

   https://doi.org/10.1109/DAC18072.2020.9218654  

   Zheng, Hao ; Wang, Ke ; Louri, Ahmed ( July 2020 , 57th ACM/IEEE Design Automation Conference (DAC))

   null (Ed.)

   Heterogeneous manycore architectures are deployed to simultaneously run multiple and diverse applications. This requires various computing capabilities (CPUs, GPUs, and accelerators), and an efficient network-on-chip (NoC) architecture to concurrently handle diverse application communication behavior. However, supporting the concurrent communication requirements of diverse applications is challenging due to the dynamic application mapping, the complexity of handling distinct communication patterns and limited on-chip resources. In this paper, we propose Adapt-NoC, a versatile and flexible NoC architecture for chiplet-based manycore architectures, consisting of adaptable routers and links. Adapt-NoC can dynamically allocate disjoint regions of the NoC, called subNoCs, for concurrently-running applications, each of which can be optimized for different communication behavior. The adaptable routers and links are capable of providing various subNoC topologies, satisfying different latency and bandwidth requirements of various traffic patterns (e.g. all-to-all, one-to-many). Full system simulation shows that AdaptNoC can achieve 31% latency reduction, 24% energy saving and 10% execution time reduction on average, when compared to prior designs. 

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2. Reconfigurable Network-on-Chip Security Architecture

   https://doi.org/10.1145/3406661  

   Charles, Subodha ; Mishra, Prabhat ( October 2020 , ACM Transactions on Design Automation of Electronic Systems)

   null (Ed.)

   Growth of the Internet-of-things has led to complex system-on-chips (SoCs) being used in the edge devices in IoT applications. The increased complexity is demanding designers to consider several critical factors, such as dynamic requirement changes, long application life, mass production, and tight time-to-market deadlines. These requirements lead to more complex security concerns. SoC manufacturers outsource some of the intellectual property cores integrated on the SoC to untrusted third-party vendors. The untrusted intellectual properties can contain malicious implants, which can launch attacks using the resources provided by the on-chip interconnection network, commonly known as the network-on-chip (NoC). Existing efforts on securing NoC have considered lightweight encryption, authentication, and other attack detection mechanisms such as denial-of-service and buffer overflows. Unfortunately, these approaches focus on designing statically optimized security solutions. As a result, they are not suitable for many IoT systems with long application life and dynamic requirement changes. There is a critical need to design reconfigurable security architectures that can be dynamically tuned based on changing requirements. In this article, we propose a tier-based reconfigurable security architecture that can adapt to different use-case scenarios. We explore how to design an efficient reconfigurable architecture that can support three popular NoC security mechanisms (encryption, authentication, and denial-of-service attack detection and localization) and implement suitable dynamic reconfiguration techniques. We evaluate our proposed framework by running standard benchmarks enabling different tiers of security and provide a comprehensive analysis of how different levels of security can affect application performance, energy efficiency, and area overhead. 

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3. An Energy-Efficient Network-on-Chip Design using Reinforcement Learning

   https://doi.org/10.1145/3316781.3317768  

   Zheng, Hao ; Louri, Ahmed ( June 2019 , 56th ACM/IEEE Design Automation Conference (DAC))

   The design space for energy-efficient Network-on-Chips (NoCs) has expanded significantly comprising a number of techniques. The simultaneous application of these techniques to yield maximum energy efficiency requires the monitoring of a large number of system parameters which often results in substantial engineering efforts and complicated control policies. This motivates us to explore the use of reinforcement learning (RL) approach that automatically learns an optimal control policy to improve NoC energy efficiency. First, we deploy power-gating (PG) and dynamic voltage and frequency scaling (DVFS) to simultaneously reduce both static and dynamic power. Second, we use RL to automatically explore the dynamic interactions among PG, DVFS, and system parameters, learn the critical system parameters contained in the router and cache, and eventually evolve optimal per-router control policies that significantly improve energy efficiency. Moreover, we introduce an artificial neural network (ANN) to efficiently implement the large state-action table required by RL. Simulation results using PARSEC benchmark show that the proposed RL approach improves power consumption by 26%, while improving system performance by 7%, as compared to a combined PG and DVFS design without RL. Additionally, the ANN design yields 67% area reduction, as compared to a conventional RL implementation. 

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4. E2M: an energy-efficient middleware for computer vision applications on autonomous mobile robots

   https://doi.org/10.1145/3318216.3363302  

   Liu, Liangkai ; Chen, Jiamin ; Brocanelli, Marco ; Shi, Weisong ( November 2019 , SEC '19: Proceedings of the 4th ACM/IEEE Symposium on Edge Computing)

   Autonomous mobile robots (AMRs) have been widely utilized in industry to execute various on-board computer-vision applications including autonomous guidance, security patrol, object detection, and face recognition. Most of the applications executed by an AMR involve the analysis of camera images through trained machine learning models. Many research studies on machine learning focus either on performance without considering energy efficiency or on techniques such as pruning and compression to make the model more energy-efficient. However, most previous work do not study the root causes of energy inefficiency for the execution of those applications on AMRs. The computing stack on an AMR accounts for 33% of the total energy consumption and can thus highly impact the battery life of the robot. Because recharging an AMR may disrupt the application execution, it is important to efficiently utilize the available energy for maximized battery life. In this paper, we first analyze the breakdown of power dissipation for the execution of computer-vision applications on AMRs and discover three main root causes of energy inefficiency: uncoordinated access to sensor data, performance-oriented model inference execution, and uncoordinated execution of concurrent jobs. In order to fix these three inefficiencies, we propose E2M, an energy-efficient middleware software stack for autonomous mobile robots. First, E2M regulates the access of different processes to sensor data, e.g., camera frames, so that the amount of data actually captured by concurrently executing jobs can be minimized. Second, based on a predefined per-process performance metric (e.g., safety, accuracy) and desired target, E2M manipulates the process execution period to find the best energy-performance trade off. Third, E2M coordinates the execution of the concurrent processes to maximize the total contiguous sleep time of the computing hardware for maximized energy savings. We have implemented a prototype of E2M on a real-world AMR. Our experimental results show that, compared to several baselines, E2M leads to 24% energy savings for the computing platform, which translates into an extra 11.5% of battery time and 14 extra minutes of robot runtime, with a performance degradation lower than 7.9% for safety and 1.84% for accuracy. 

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5. Coordinated CTA Combination and Bandwidth Partitioning for GPU Concurrent Kernel Execution

   https://doi.org/10.1145/3326124  

   Lin, Zhen ; Dai, Hongwen ; Mantor, Michael ; Zhou, Huiyang ( August 2019 , ACM Transactions on Architecture and Code Optimization)

   null (Ed.)

   Contemporary GPUs support multiple kernels to run concurrently on the same streaming multiprocessors (SMs). Recent studies have demonstrated that such concurrent kernel execution (CKE) improves both resource utilization and computational throughput. Most of the prior works focus on partitioning the GPU resources at the cooperative thread array (CTA) level or the warp scheduler level to improve CKE. However, significant performance slowdown and unfairness are observed when latency-sensitive kernels co-run with bandwidth-intensive ones. The reason is that bandwidth over-subscription from bandwidth-intensive kernels leads to much aggravated memory access latency, which is highly detrimental to latency-sensitive kernels. Even among bandwidth-intensive kernels, more intensive kernels may unfairly consume much higher bandwidth than less-intensive ones. In this article, we first make a case that such problems cannot be sufficiently solved by managing CTA combinations alone and reveal the fundamental reasons. Then, we propose a coordinated approach for CTA combination and bandwidth partitioning. Our approach dynamically detects co-running kernels as latency sensitive or bandwidth intensive. As both the DRAM bandwidth and L2-to-L1 Network-on-Chip (NoC) bandwidth can be the critical resource, our approach partitions both bandwidth resources coordinately along with selecting proper CTA combinations. The key objective is to allocate more CTA resources for latency-sensitive kernels and more NoC/DRAM bandwidth resources to NoC-/DRAM-intensive kernels. We achieve it using a variation of dominant resource fairness (DRF). Compared with two state-of-the-art CKE optimization schemes, SMK [52] and WS [55], our approach improves the average harmonic speedup by 78% and 39%, respectively. Even compared to the best possible CTA combinations, which are obtained from an exhaustive search among all possible CTA combinations, our approach improves the harmonic speedup by up to 51% and 11% on average. 

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