엣지 클라우드 환경을 위한 연산 오프로딩 시스템

학위논문(박사)--서울대학교 대학원 :공과대학 전기·정보공학부,2020. 2. 문수묵.The purpose of my dissertation is to build lightweight edge computing systems which provide seamless offloading services even when users move across multiple edge servers. I focused on two specific application domains: 1) web applications and 2) DNN applications. I propose an edge computing system which offload computations from web-supported devices to edge servers. The proposed system exploits the portability of web apps, i.e., distributed as source code and runnable without installation, when migrating the execution state of web apps. This significantly reduces the complexity of state migration, allowing a web app to migrate within a few seconds. Also, the proposed system supports offloading of webassembly, a standard low-level instruction format for web apps, having achieved up to 8.4x speedup compared to offloading of pure JavaScript codes. I also propose incremental offloading of neural network (IONN), which simultaneously offloads DNN execution while deploying a DNN model, thus reducing the overhead of DNN model deployment. Also, I extended IONN to support large-scale edge server environments by proactively migrating DNN layers to edge servers where mobile users are predicted to visit. Simulation with open-source mobility dataset showed that the proposed system could significantly reduce the overhead of deploying a DNN model.본 논문의 목적은 사용자가 이동하는 동안에도 원활한 연산 오프로딩 서비스를 제공하는 경량 엣지 컴퓨팅 시스템을 구축하는 것입니다. 웹 어플리케이션과 인공신경망 (DNN: Deep Neural Network) 이라는 두 가지 어플리케이션 도메인에서 연구를 진행했습니다. 첫째, 웹 지원 장치에서 엣지 서버로 연산을 오프로드하는 엣지 컴퓨팅 시스템을 제안합니다. 제안된 시스템은 웹 앱의 실행 상태를 마이그레이션 할 때 웹 앱의 높은 이식성(소스 코드로 배포되고 설치하지 않고 실행할 수 있음)을 활용합니다. 이를 통해 상태 마이그레이션의 복잡성이 크게 줄여서 웹 앱이 몇 초 내에 마이그레이션 될 수 있습니다. 또한, 제안된 시스템은 웹 어플리케이션을 위한 표준 저수준 인스트럭션인 웹 어셈블리 오프로드를 지원하여 순수한 JavaScript 코드 오프로드와 비교하여 최대 8.4 배의 속도 향상을 달성했습니다. 둘째, DNN 어플리케이션을 엣지 서버에 배포할 때, DNN 모델을 전송하는 동안 DNN 연산을 오프로드 하여 빠르게 성능향상을 달성할 수 있는 점진적 오프로드 방식을 제안합니다. 또한, 모바일 사용자가 방문 할 것으로 예상되는 엣지 서버로 DNN 레이어를 사전에 마이그레이션하여 콜드 스타트 성능을 향상시키는 방식을 제안 합니다. 오픈 소스 모빌리티 데이터셋을 이용한 시뮬레이션에서, DNN 모델을 배포하면서 발생하는 성능 저하를 제안 하는 방식이 크게 줄일 수 있음을 확인하였습니다.Chapter 1. Introduction 1 1.1 Offloading Web App Computations to Edge Servers 1 1.2 Offloading DNN Computations to Edge Servers 3 Chapter 2. Seamless Offloading of Web App Computations 7 2.1 Motivation: Computation-Intensive Web Apps 7 2.2 Mobile Web Worker System 10 2.2.1 Review of HTML5 Web Worker 10 2.2.2 Mobile Web Worker System 11 2.3 Migrating Web Worker 14 2.3.1 Runtime State of Web Worker 15 2.3.2 Snapshot of Mobile Web Worker 16 2.3.3 End-to-End Migration Process 21 2.4 Evaluation 22 2.4.1 Experimental Environment 22 2.4.2 Migration Performance 24 2.4.3 Application Execution Performance 27 Chapter 3. IONN: Incremental Offloading of Neural Network Computations 30 3.1 Motivation: Overhead of Deploying DNN Model 30 3.2 Background 32 3.2.1 Deep Neural Network 33 3.2.2 Offloading of DNN Computations 33 3.3 IONN For DNN Edge Computing 35 3.4 DNN Partitioning 37 3.4.1 Neural Network (NN) Execution Graph 38 3.4.2 Partitioning Algorithm 40 3.4.3 Handling DNNs with Multiple Paths. 43 3.5 Evaluation 45 3.5.1 Experimental Environment 45 3.5.2 DNN Query Performance 46 3.5.3 Accuracy of Prediction Functions 48 3.5.4 Energy Consumption. 49 Chapter 4. PerDNN: Offloading DNN Computations to Pervasive Edge Servers 51 4.1 Motivation: Cold Start Issue 51 4.2 Proposed Offloading System: PerDNN 52 4.2.1 Edge Server Environment 53 4.2.2 Overall Architecture 54 4.2.3 GPU-aware DNN Partitioning 56 4.2.4 Mobility Prediction 59 4.3 Evaluation 63 4.3.1 Performance Gain of Single Client 64 4.3.2 Large-Scale Simulation 65 Chapter 5. RelatedWorks 73 Chapter 6. Conclusion. 78 Chapter 5. RelatedWorks 73 Chapter 6. Conclusion 78 Bibliography 80Docto

ES6 자바스크립트의 스냅샷 기반 마이그레이션

학위논문(석사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2021.8. 문수묵.최근 웹 플랫폼 및 자바스크립트의 인기와 함께, 자바스크립트로 작성된 프로그램을 위한 앱 마이그레이션 기술이 연구된 바 있다. 이는 이종의 기기 간에 연속적인 워크플로우를 제공해 새로운 사용자 경험을 제공하는 기술을 일컫는다. 여러 선행 연구에서 스냅샷 기반 방법론을 사용해 앱의 런타임 상태를 텍스트 형태로 직렬화 및 복원하는 시도를 했다. 그러나, 기존 연구들은 구 버전 자바스크립트 상에서 진행됐다는 한계가 있다. 이에 비해 ECMAScript2015 (ES6) 업데이트 이후 자바스크립트에 다양한 기능이 도입되었기 때문에, 기존 방법들은 오늘날 real-world 애플리케이션을 마이그레이션하기 어렵다. 본 논문은 [19]에서 소개된 우리의 프레임워크를 소개한다. 우리는 선행 연구에서 다뤄지지 않은 block scope, module, class syntax와 같은 ES6의 주요 기능을 분석했으며 이러한 새로운 기능을 사용하는 앱을 마이그레이션 하기 위한 알고리즘을 제안했다. 또한, 우리는 최신 자바스크립트 엔진에 대한 분석을 통해 실행 중인 자바스크립트 프로그램의 런타임 상태를 scope tree라는 자료구조 상에 직렬화하고, 후처리를 거친 scope tree로부터 스냅샷 코드를 생성했다. 이러한 방법론을 V8 자바스크립트 엔진인 상에 구현했으며, 복잡한 최신 자바스크립트 기능을 사용하는 벤치마크 프로그램에 대해 실험했다. 실험 결과를 통해 이러한 방법이 모바일 기기 간에 5개의 벤치마크 프로그램을 성공적으로 마이그레이션 시킨다는 것을 보였다. 복잡도가 가장 높은 앱 (ML 벤치마크, 소스 코드 크기 213KB)에 대한 실험에서 프레임워크로 인한 시간 부하를 측정한 결과, X86 랩톱에서 200ms 미만, ARM 기반 임베디드 보드에서 800ms 미만이었다. 이러한 결과를 통해 자원이 제한된 IoT 기기 등에 대한 적용 가능성을 검증했으며, 추가적으로 프레임워크의 활용 방안 및 향후 연구 방향에 대해 논의한다.With the growing popularity of the web platform and JavaScript, an interesting user experience called application (app) migration has been proposed for JavaScript programs. To enable a non-breaking workflow across different devices, recent studies have proposed snapshot-based techniques in which an app’s runtime state is serialized into a text form that can be restored back later. A limitation of existing literature, however, is that they are based on old JavaScript specifications. Since major updates introduced by ECMASCript2015 (a.k.a. ES6), JavaScript supports various features that cannot be migrated correctly with existing methods. Some of these features are heavily used in today’s real-world apps and thus greatly reduces the scope of previous works. In this thesis, I will mainly introduce my work presented in [19]. In the paper, we analyzed ES6 features such as block scopes, modules, and class syntax that were previously uncovered in app migration. We presented an algorithm that enables migration of apps implemented with these new features. Based on the standards adopted in modern JavaScript engines, our approach serializes a running program into a scope tree and reorganizes it for snapshot code generation. We implemented our idea on the open source V8 engine and experiment with complex benchmark programs of modern JavaScript. Results showed that our approach correctly migrates 5 target programs between mobile devices. Our framework could migrate the most complex app of source code size 213KB in less than 200ms in a X86 laptop and 800ms in an embedded ARM board, showing feasibility in resource-constrained IoT devices. I will also discuss possible use cases and research directions and conclude.Chapter 1. Introduction 1 1.1. JavaScript App Migration 1 1.2. Purpose of Research 2 Chapter 2. Background 4 2.1. Snapshot-based Approach 4 2.2. Function Closure and Scope Tree 6 2.3. Limitations of Previous Works 6 Chapter 3. Proposed Approach 10 3.1. Module Profiling 10 3.2. Migrating Modified Built-in Objects 11 3.3. Scope Tree Building 11 3.4. Syntax-Aware Tree Re-ordering 12 3.5. Tree Partitioning 13 3.6. Snapshot Code Generation 13 Chapter 4. Evaluation 17 4.1. Implementation and Setup 17 4.2. Scope Tree Analysis 18 4.3. Snapshot Code Sizes 19 4.4. Framework Time Overhead 20 Chapter 5. Discussion 22 5.1. Limitations 22 5.2. Alternative Approach 22 5.3. Potential Use Cases 23 Chapter 6. Conclusion 24 Bibliography 25 Abstract in Korean 27석

Universal Mobile Service Execution Framework for Device-To-Device Collaborations

There are high demands of effective and high-performance of collaborations between mobile devices in the places where traditional Internet connections are unavailable, unreliable, or significantly overburdened, such as on a battlefield, disaster zones, isolated rural areas, or crowded public venues. To enable collaboration among the devices in opportunistic networks, code offloading and Remote Method Invocation are the two major mechanisms to ensure code portions of applications are successfully transmitted to and executed on the remote platforms. Although these domains are highly enjoyed in research for a decade, the limitations of multi-device connectivity, system error handling or cross platform compatibility prohibit these technologies from being broadly applied in the mobile industry. To address the above problems, we designed and developed UMSEF - an Universal Mobile Service Execution Framework, which is an innovative and radical approach for mobile computing in opportunistic networks. Our solution is built as a component-based mobile middleware architecture that is flexible and adaptive with multiple network topologies, tolerant for network errors and compatible for multiple platforms. We provided an effective algorithm to estimate the resource availability of a device for higher performance and energy consumption and a novel platform for mobile remote method invocation based on declarative annotations over multi-group device networks. The experiments in reality exposes our approach not only achieve the better performance and energy consumption, but can be extended to large-scaled ubiquitous or IoT systems

Liquid stream processing on the web: a JavaScript framework

The Web is rapidly becoming a mature platform to host distributed applications. Pervasive computing application running on the Web are now common in the era of the Web of Things, which has made it increasingly simple to integrate sensors and microcontrollers in our everyday life. Such devices are of great in- terest to Makers with basic Web development skills. With them, Makers are able to build small smart stream processing applications with sensors and actuators without spending a fortune and without knowing much about the technologies they use. Thanks to ongoing Web technology trends enabling real-time peer-to- peer communication between Web-enabled devices, Web browsers and server- side JavaScript runtimes, developers are able to implement pervasive Web ap- plications using a single programming language. These can take advantage of direct and continuous communication channels going beyond what was possible in the early stages of the Web to push data in real-time. Despite these recent advances, building stream processing applications on the Web of Things remains a challenging task. On the one hand, Web-enabled devices of different nature still have to communicate with different protocols. On the other hand, dealing with a dynamic, heterogeneous, and volatile environment like the Web requires developers to face issues like disconnections, unpredictable workload fluctuations, and device overload. To help developers deal with such issues, in this dissertation we present the Web Liquid Streams (WLS) framework, a novel streaming framework for JavaScript. Developers implement streaming operators written in JavaScript and may interactively and dynamically define a streaming topology. The framework takes care of deploying the user-defined operators on the available devices and connecting them using the appropriate data channel, removing the burden of dealing with different deployment environments from the developers. Changes in the semantic of the application and in its execution environment may be ap- plied at runtime without stopping the stream flow. Like a liquid adapts its shape to the one of its container, the Web Liquid Streams framework makes streaming topologies flow across multiple heterogeneous devices, enabling dynamic operator migration without disrupting the data flow. By constantly monitoring the execution of the topology with a hierarchical controller infrastructure, WLS takes care of parallelising the operator execution across multiple devices in case of bottlenecks and of recovering the execution of the streaming topology in case one or more devices disconnect, by restarting lost operators on other available devices

Optimizing task allocation for edge compute micro-clusters

There are over 30 billion devices at the network edge. This is largely driven by the unprecedented growth of the Internet-of-Things (IoT) and 5G technologies. These devices are being used in various applications and technologies, including but not limited to smart city systems, innovative agriculture management systems, and intelligent home systems. Deployment issues like networking and privacy problems dictate that computing should occur close to the data source at or near the network edge. Edge and fog computing are recent decentralised computing paradigms proposed to augment cloud services by extending computing and storage capabilities to the network’s edge to enable executing computational workloads locally. The benefits can help to solve issues such as reducing the strain on networking backhaul, improving network latency and enhancing application responsiveness. Many edge and fog computing deployment solutions and infrastructures are being employed to deliver cloud resources and services at the edge of the network — for example, cloudless and mobile edge computing. This thesis focuses on edge micro-cluster platforms for edge computing. Edge computing micro-cluster platforms are small, compact, and decentralised groups of interconnected computing resources located close to the edge of a network. These micro-clusters can typically comprise a variety of heterogeneous but resource-constrained computing resources, such as small compute nodes like Single Board Computers (SBCs), storage devices, and networking equipment deployed in local area networks such as smart home management. The goal of edge computing micro-clusters is to bring computation and data storage closer to IoT devices and sensors to improve the performance and reliability of distributed systems. Resource management and workload allocation represent a substantial challenge for such resource-limited and heterogeneous micro-clusters because of diversity in system architecture. Therefore, task allocation and workload management are complex problems in such micro-clusters. This thesis investigates the feasibility of edge micro-cluster platforms for edge computation. Specifically, the thesis examines the performance of micro-clusters to execute IoT applications. Furthermore, the thesis involves the evaluation of various optimisation techniques for task allocation and workload management in edge compute micro-cluster platforms. This thesis involves the application of various optimisation techniques, including simple heuristics-based optimisations, mathematical-based optimisation and metaheuristic optimisation techniques, to optimise task allocation problems in reconfigurable edge computing micro-clusters. The implementation and performance evaluations take place in a configured edge realistic environment using a constructed micro-cluster system comprised of a group of heterogeneous computing nodes and utilising a set of edge-relevant applications benchmark. The research overall characterises and demonstrates a feasible use case for micro-cluster platforms for edge computing environments and provides insight into the performance of various task allocation optimisation techniques for such micro-cluster systems

Mango: A model-driven approach to engineering green Mobile Cloud Applications

With the resource constrained nature of mobile devices and the resource abundant offerings of the cloud, several promising optimisation techniques have been proposed by the green computing research community. Prominent techniques and unique methods have been developed to offload resource/computation intensive tasks from mobile devices to the cloud. Most of the existing offloading techniques can only be applied to legacy mobile applications as they are motivated by existing systems. Consequently, they are realised with custom runtimes which incur overhead on the application. Moreover, existing approaches which can be applied to the software development phase, are difficult to implement (based on manual process) and also fall short of overall (mobile to cloud) efficiency in software qualityattributes or awareness of full-tier (mobile to cloud) implications.To address the above issues, the thesis proposes a model-driven architecturefor integration of software quality with green optimisation in Mobile Cloud Applications (MCAs), abbreviated as Mango architecture. The core aim of the architecture is to present an approach which easily integrates software quality attributes (SQAs) with the green optimisation objective of Mobile Cloud Computing (MCC). Also, as MCA is an application domain which spans through the mobile and cloud tiers; the Mango architecture, therefore, takesinto account the specification of SQAs across the mobile and cloud tiers, for overall efficiency. Furthermore, as a model-driven architecture, models can be built for computation intensive tasks and their SQAs, which in turn drives the development – for development efficiency. Thus, a modelling framework (called Mosaic) and a full-tier test framework (called Beftigre) were proposed to automate the architecture derivation and demonstrate the efficiency of Mango approach. By use of real world scenarios/applications, Mango has been demonstrated to enhance the MCA development process while achieving overall efficiency in terms of SQAs (including mobile performance and energy usage compared to existing counterparts)

A patient agent controlled customized blockchain based framework for internet of things

Although Blockchain implementations have emerged as revolutionary technologies for various industrial applications including cryptocurrencies, they have not been widely deployed to store data streaming from sensors to remote servers in architectures known as Internet of Things. New Blockchain for the Internet of Things models promise secure solutions for eHealth, smart cities, and other applications. These models pave the way for continuous monitoring of patient’s physiological signs with wearable sensors to augment traditional medical practice without recourse to storing data with a trusted authority. However, existing Blockchain algorithms cannot accommodate the huge volumes, security, and privacy requirements of health data. In this thesis, our first contribution is an End-to-End secure eHealth architecture that introduces an intelligent Patient Centric Agent. The Patient Centric Agent executing on dedicated hardware manages the storage and access of streams of sensors generated health data, into a customized Blockchain and other less secure repositories. As IoT devices cannot host Blockchain technology due to their limited memory, power, and computational resources, the Patient Centric Agent coordinates and communicates with a private customized Blockchain on behalf of the wearable devices. While the adoption of a Patient Centric Agent offers solutions for addressing continuous monitoring of patients’ health, dealing with storage, data privacy and network security issues, the architecture is vulnerable to Denial of Services(DoS) and single point of failure attacks. To address this issue, we advance a second contribution; a decentralised eHealth system in which the Patient Centric Agent is replicated at three levels: Sensing Layer, NEAR Processing Layer and FAR Processing Layer. The functionalities of the Patient Centric Agent are customized to manage the tasks of the three levels. Simulations confirm protection of the architecture against DoS attacks. Few patients require all their health data to be stored in Blockchain repositories but instead need to select an appropriate storage medium for each chunk of data by matching their personal needs and preferences with features of candidate storage mediums. Motivated by this context, we advance third contribution; a recommendation model for health data storage that can accommodate patient preferences and make storage decisions rapidly, in real-time, even with streamed data. The mapping between health data features and characteristics of each repository is learned using machine learning. The Blockchain’s capacity to make transactions and store records without central oversight enables its application for IoT networks outside health such as underwater IoT networks where the unattended nature of the nodes threatens their security and privacy. However, underwater IoT differs from ground IoT as acoustics signals are the communication media leading to high propagation delays, high error rates exacerbated by turbulent water currents. Our fourth contribution is a customized Blockchain leveraged framework with the model of Patient-Centric Agent renamed as Smart Agent for securely monitoring underwater IoT. Finally, the smart Agent has been investigated in developing an IoT smart home or cities monitoring framework. The key algorithms underpinning to each contribution have been implemented and analysed using simulators.Doctor of Philosoph

Earth Observation Open Science and Innovation

geospatial analytics; social observatory; big earth data; open data; citizen science; open innovation; earth system science; crowdsourced geospatial data; citizen science; science in society; data scienc