基于Docker技术的GUI应用的在线迁移研究

GUI应用在桌面环境中占据主流,在线迁移GUI应用能够提升用户体验.然而,当今广泛使用的X窗口系统所定义的协议十分复杂,不利于GUI进程的在线迁移.另外,如果两台机器的运行时环境不一致,将会导致迁移失败.因此至今未有实现GUI应用的在线迁移.近年来,Wayland作为新的图形接口协议面世,其中规定软件图形渲染由GUI客户端负责,这为迁移工作带来极大的便利.而当今热门的Docker容器技术则能把Wayland GUI应用及其运行时库打包,确保运行时环境的一致性.当迁移发生时,整个容器都会被迁移至目标机器继续运行.本文开发了相应的处理Wayland协议模块,并在CRIU工具的基础上实现了重建Wayland状态.通过实验证明,本文方案是可行的,容易推广到其他的GUI应用.     

Securely outsourcing the ciphertext-policy attribute-based encryption

Attribute-based Encryption (ABE) is a new and promising public key encryption that allows fine-grained authorization on data based on user attributes. Such property is favorable for multiple applications that require encrypted storage or access control on data, in particular: eHealth applications. However, ABE schemes are known not to be efficient in the encryption phase because ciphertext size and the time required to encrypt grow with the complexity of the access policy. Such drawback is critical in the context of pervasive computing, for instance, in the Internet of Things, where data producers are usually resource-constrained devices, e.g. smart phones or sensing platforms. In this work, we propose OEABE standing for Outsourcing mechanism for the Encryption of Ciphertext-Policy ABE (CP-ABE). We show how a user can offload expensive operations of CP-ABE encryption to a semi-trusted party in a secure manner. Our proposed mechanism requires only one exponentiation on resource-constrained devices. We provide also an informal security analysis of possible attacks from a semi-honest adversary against the proposed solution. To demonstrate the performance gains of our mechanism, we first conducted a performance estimation on an emulated Wismote sensor platform. Then, we implemented our proposal and did comparison to an existing implementation of CP-ABE on a laptop.     

Moving huge scientific datasets over the Internet

Modern scientific experiments can generate hundreds of gigabytes to terabytes or even petabytes of data that may be maintained in large numbers of relatively small files. Frequently, these data must be disseminated to remote collaborators or computational centers for data analysis. Moving this dataset with high performance and strong robustness and providing a simple interface for users are challenging tasks. We present a data transfer framework comprising a high‐performance data transfer library based on GridFTP, an extensible data scheduler with four data scheduling policies, and a GUI that allows users to transfer their dataset easily, reliably, and securely. This system incorporates automatic tuning mechanisms to select at runtime the number of concurrent threads to be used for transfers. Also included are restart mechanisms for handling client, network, and server failures. Experimental results indicate that our data transfer system can significantly improve data transfer performance and can recover well from failures. Copyright © 2011 John Wiley & Sons, Ltd.     

面向物联网应用的SoC安全检查架构设计

物联网（IoT）应用的快速发展和软硬件开源化趋势使得IoT设备所面临的硬件安全威胁日益严峻,尤其是利用运行时条件触发的系统级攻击,很难通过传统测试方法进行检测和防御,需要提供运行时安全检查机制。分析IoT系统芯片面临的安全威胁,结合数据加密传输路径中的攻击、任务流和检查内容,设计4条功能完整性安全检查策略,搭建SoC安全策略检查架构并植入运行时触发硬件木马。仿真结果显示,运行时策略检查状态机可以检查出加密核、内存和UART接口的功能完整性问题,并通过发送错误中断信号进行反馈,证明了所设计的系统级安全策略检查架构的正确性与有效性。     

基于多层次特征融合的图像超分辨率重建

深度卷积神经网络显著改进了单图像超分辨率的性能.更深的网络往往能获得更好的性能.但是,加深网络会导致参数量急剧增加,限制了它在资源受限设备上的应用,比如智能手机.提出了一个融合多层次特征的轻量级单图像超分辨率网络,主要构件是双层嵌套残差块.为了更好地提取特征,减少参数量,每个残差块采用对称结构:先两次扩张,然后两次压缩通道数.在残差块中,通过添加自相关权重单元,加权融合不同通道的特征信息.实验证明,该方法显著优于当前同类方法.     

Towards modeling and runtime verification of self-organizing systems

According to the fact that the intrinsic dynamism of self-organizing systems challenges the existing methods of engineering for modeling reliable complex systems, in this paper, we propose a new formal-based method to model self-organizing systems. The capabilities of the proposed method which are used to address several challenges in design, development and analysis of self-organizing systems are: modularity and robustness, decentralized control and scalability, required adaptation types, flexible and adaptive control mechanism, separation of adaptation and business logic, and safe adaptation. To evaluate the proposed method, we use self-organizing traffic management system as a case study and exploit the proposed method for modeling this dynamic system. Moreover, we propose and employ a novel policy-based runtime verification mechanism to ensure that the safety properties are satisfied by the implementation at runtime. We provide our case study prototype using Java and the Ponder2 toolkit and apply our runtime verification method to show its proper reaction capabilities to the property violations. This benefit is the result of using dynamic policies in our method to control the behavior of systems.     

New strategies for stochastic resource-constrained project scheduling

We study the stochastic resource-constrained project scheduling problem or SRCPSP, where project activities have stochastic durations. A solution is a scheduling policy, and we propose a new class of policies that is a generalization of most of the classes described in the literature. A policy in this new class makes a number of a priori decisions in a preprocessing phase, while the remaining scheduling decisions are made online. A two-phase local search algorithm is proposed to optimize within the class. Our computational results show that the algorithm has been efficiently tuned toward finding high-quality solutions and that it outperforms all existing algorithms for large instances. The results also indicate that the optimality gap even within the larger class of elementary policies is very small.     

Accurate power modeling of modern mobile application processors

The power modeling of mobile application processors (APs) is a challenging task due to their complexity. The existing power models and their associated devices have mostly been made obsolete by recent hardware developments. In this paper, we propose an enhanced power model used in modern mobile devices. The model accurately estimates the power consumption of AP component and utilizes the runtime usage information of each hardware component. We evaluated the model accuracy using various benchmarks, as well as popular smartphone applications with multiple devices that employ different APs. The evaluation shows that our model achieves the mean absolute percentage error (MAPE) of 5.1%.     

Resource and performance trade-offs in real-time embedded control systems

Embedded control systems are subject to conflicting demands: end-users ask for devices with better capabilities while strong industrial competition impose tight cost constrains that results in devices with limited resources. Current research in the multidisciplinary embedded systems discipline indicates that by combining real-time and control systems it is theoretically feasible to design resource-constrained embedded control systems capable of trading-off control performance and resource usage. This paper focuses on the implementation feasibility of recent state-of-the-art resource/performance-aware (RPA) policies that can be applied to a set of control loops that concurrently execute on a microprocessor. The objective of these policies is to improve control performance and/or to minimize resource utilization. The paper first reviews existing state-of-the-art RPA policies. Then it presents a performance evaluation framework (PEF) that permits to assess whether RPA policies can be implemented in practice. The PEF is designed using a modular approach and following the guidelines obtained by a taxonomic analysis performed on the state-of-the-art RPA policies. Finally, a case study is presented where the PEF is applied to a set of representative RPA policies. The case study reveals that the modularity of the PEF allows tailoring the framework to evaluate any specific RPA policy, which indicates that RPA policies can be implemented in practice. But it also reveals that the problem of assessing diverse RPA policies in fair conditions implies facing and solving conflicting demands by even taking decisions that may not favor equal all policies under evaluation. Nevertheless, the comparative analysis permits identifying potential benefits and drawbacks of each policy, as well as extracting design guidelines for future real-time embedded control systems theory and practice.     

基于Linux的中低端嵌入式GUI的开发

本文介绍了Linux下嵌入式GUI的发展及其在系统中的作用，研究了嵌入式GUI的设计思想，着重阐述了如何在中低端设备上实现windows风格的多进程多窗口剪切，提出了如何借助Z序和树型结构实现多窗口的管理，最后分析了所设计的GUI特点。     

MultiCL: Enabling automatic scheduling for task-parallel workloads in OpenCL

The OpenCL specification tightly binds a command queue to a specific device. For best performance, the user has to find the ideal queue-device mapping at command queue creation time, an effort that requires a thorough understanding of the underlying device architectures and kernels in the program. In this paper, we propose to add scheduling attributes to the OpenCL context and command queue objects that can be leveraged by an intelligent runtime scheduler to automatically perform ideal queuedevice mapping. Our proposed extensions enable the average OpenCL programmer to focus on the algorithm design rather than scheduling and to automatically gain performance without sacrificing programmability. As an example, we design and implement an OpenCL runtime for task-parallel workloads, called MultiCL, which efficiently schedules command queues across devices.Our case studies include the SNU benchmark suite and a real-world seismology simulation. To benefit from our runtime optimizations, users have to apply our proposed scheduler extensions to only four source lines of code, on average, in existing OpenCL applications. We evaluate both single-node and multinode experiments and also compare with SOCL, our closest related work. We show that MultiCL maps command queues to the optimal device set in most cases with negligible runtime overhead.     

Dynamic shortest path problems: Hybrid routing policies considering network disruptions

Traffic network disruptions lead to significant increases in transportation costs. We consider networks in which a number of links are vulnerable to these disruptions leading to a significantly higher travel time on these links. For these vulnerable links, we consider known link disruption probabilities and knowledge of transition probabilities for recovering from or getting into a disruption. We develop a framework based on dynamic programming in which we formulate and evaluate different known online and offline routing policies. Next to this, we develop computation-time-efficient hybrid routing policies. To test the efficiency of the different routing policies, we develop a test bed of networks based on a number of characteristics and analyze the results in terms of routes, cost performance and calculation times. Our results show that a significant part of the cost reduction can be obtained by considering only a limited part of the network in detail. The performance of our proposed hybrid policy is only slightly worse than the optimal policy.     

Hybrid power management in real time embedded systems: an interplay of DVFS and DPM techniques

Energy-aware scheduling of real time applications over multiprocessor systems is considered in this paper. Early research reports that while various energy-saving policies, for instance Dynamic Power Management (DPM) and Dynamic Voltage & Frequency scaling (DVFS) policies, perform well individually for a specific set of operating conditions, they often outperform each other under different workload and/or architecture configuration. Thus, no single policy fits perfectly all operating conditions. Instead of designing new policies for specific operating conditions, this paper proposes a generic power/energy management scheme that takes a set of well-known existing (DPM and DVFS) policies, each of which performs well for a set of conditions, and adapts at runtime to the best-performing policy for any given workload. Experiments are performed using state-of the-art DPM and DVFS policies and the results show that our proposed scheme adapts well to the changing workload and always achieves overall energy savings comparable to that of best-performing policy at any point in time.     

Toward balanced and sustainable job scheduling for production supercomputers

Job scheduling on production supercomputers is complicated by diverse demands of system administrators and amorphous characteristics of workloads. Specifically, various scheduling goals such as queuing efficiency and system utilization are usually conflicting and thus need to be balanced. Also, changing workload characteristics often impact the effectiveness of the deployed scheduling policies. Thus it is challenging to design a versatile scheduling policy that is effective in all circumstances. In this paper, we propose a novel job scheduling strategy to balance diverse scheduling goals and mitigate the impact of workload characteristics. First, we introduce metric-aware scheduling, which enables the scheduler to balance competing scheduling goals represented by different metrics such as job waiting time, fairness, and system utilization. Second, we design a scheme to dynamically adjust scheduling policies based on feedback information of monitored metrics at runtime. We evaluate our design using real workloads from supercomputer centers. The results demonstrate that our scheduling mechanism can significantly improve system performance in a balanced, sustainable fashion.     

An integrated runtime and compile-time approach for parallelizingstructured and block structured applications

In compiling applications for distributed memory machines, runtime analysis is required when data to be communicated cannot be determined at compile-time. One such class of applications requiring runtime analysis is block structured codes. These codes employ multiple structured meshes, which may be nested (for multigrid codes) and/or irregularly coupled (called multiblock or irregularly coupled regular mesh problems). In this paper, we present runtime and compile-time analysis for compiling such applications on distributed memory parallel machines in an efficient and machine-independent fashion. We have designed and implemented a runtime library which supports the runtime analysis required. The library is currently implemented on several different systems. We have also developed compiler analysis for determining data access patterns at compile time and inserting calls to the appropriate runtime routines. Our methods can be used by compilers for HPF-like parallel programming languages in compiling codes in which data distribution, loop bounds and/or strides are unknown at compile-time. To demonstrate the efficacy of our approach, we have implemented our compiler analysis in the Fortran 90D/HPF compiler developed at Syracuse University. We have experimented with a multi-bloc Navier-Stokes solver template and a multigrid code. Our experimental results show that our primitives have low runtime communication overheads and the compiler parallelized codes perform within 20% of the codes parallelized by manually inserting calls to the runtime library     

PAM: an efficient power-aware multilevel cache policy to reduce energy consumption of storage systems

Energy consumption is one of the most significant aspects of large-scale storage systems where multilevel caches are widely used. In a typical hierarchical storage structure, upper-level storage serves as a cache for the lower level, forming a distributed multilevel cache system. In the past two decades, several classic LRU-based multilevel cache policies have been proposed to improve the overall I/O performance of storage systems. However, few power-aware multilevel cache policies focus on the storage devices in the bottom level, which consume more than 27% of the energy of the whole system [1]. To address this problem, we propose a novel power-aware multilevel cache (PAM) policy that can reduce the energy consumption of high-performance and I/O bandwidth storage devices. In our PAM policy, an appropriate number of cold dirty blocks in the upper level cache are identified and selected to flush directly to the storage devices, providing high probability extension of the lifetime of disks in standby mode. To demonstrate the effectiveness of our proposed policy, we conduct several simulations with real-world traces. Compared to existing popular cache schemes such as PALRU, PB-LRU, and Demote, PAM reduces power consumption by up to 15% under different I/O workloads, and improves energy efficiency by up to 50.5%.     

Hierarchical GUI test case generation using automated planning

The widespread use of GUIs for interacting with software is leading to the construction of more and more complex GUIs. With the growing complexity come challenges in testing the correctness of a GUI and its underlying software. We present a new technique to automatically generate test cases for GUIs that exploits planning, a well-developed and used technique in artificial intelligence. Given a set of operators, an initial state, and a goal state, a planner produces a sequence of the operators that will transform the initial state to the goal state. Our test case generation technique enables efficient application of planning by first creating a hierarchical model of a GUI based on its structure. The GUI model consists of hierarchical planning operators representing the possible events in the GUI. The test designer defines the preconditions and effects of the hierarchical operators, which are input into a plan-generation system. The test designer also creates scenarios that represent typical initial and goal states for a GUI user. The planner then generates plans representing sequences of GUI interactions that a user might employ to reach the goal state from the initial state. We implemented our test case generation system, called Planning Assisted Tester for Graphical User Interface Systems (PATHS) and experimentally evaluated its practicality and effectiveness. We describe a prototype implementation of PATHS and report on the results of controlled experiments to generate test cases for Microsoft's WordPad     

MIDP2.0安全性分析

J2ME平台是一种应用于资源受限的消费类电子设备的Java运行时环境，应用广泛；然而，深受众多移动终端支持的MIDP1．0缺乏足够的安全机制，使得这些设备上的信息安全受到威胁和攻击，这种状况有望在MIDP2．0中得到改善。首先简要介绍了J2ME和MIDP的概念，讨论了移动环境下支持MIDP1．0的设备受到的安全威胁和攻击，阐述了MIDP2．0规范中新增的安全机制和特征——主要表现在增加了安全的网络协议（如SSL）和采用了对MIDlet应用程序签名的策略等，分析了这些增强的安全机制如何防止和抵御对敏感信息的威胁和攻击，从而得出结论，MIDP2．0虽然仍然存在威胁和攻击，但在安全性方面比MIDP1．0有了很大的提高。     

基于Linux的嵌入式GUI系统设计分析

随着技术的发展,嵌入式系统要求使用图形化界面便于用户的操作。本文从系统体系结构出发,讨论了GUI设计中涉及的几个重要方面,包括消息循环、多窗口管理、控件／控件类和输入／输出抽象层的基本概念和设计要点。