DisCusS : desenvolvendo um serviço de concenso generico, simples e modular

Orientador: Edmundo Roberto Mauro MadeiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Esta dissertação trata do processo de engenharia de um serviço de detecção de falhas compatível com FT-CORBA, a especm.cação para tolerância a falhas em CORBA, e de um serviço de consenso distribuído. Os serviços são independentes e fornecem diferentes propriedades para a aplicação cliente, dependendo dos módulos, com implementaçães de algoritmos diferentes, selecionados para uma instanciação destes serviços. A arquitetura dos serviços é tal que a aplicação cliente não toma conhecimento dos algoritmos de detecção e consenso sendo executados, acessando-os por uma interface genérica. Com o intuito de facilitar a escolha dos módulos dos serviços, apresentamos um pequeno estudo comparativo da influência de detectores de falhas adaptativos, aqueles que se adaptam para prover melhor qualidade de serviço na detecção, e não adaptativos sobre o desempenho dos algoritmos de consenso distribuídoAbstract: This thesis is on the process of development of a distributed consensus service and its fault detection service, being the last one, compliant with FT -CORBA, the Fault Tolerant CORBA specification. These services are independent and, depending on the selected modules, offer different properties to client applications. The presented architecture is defined in such a way that client applications do not know which algorithms are running, both for detection and for consensus, just accessing them through a generic interface. To make easier the task of selecting modules in the services, we also present a comparative study of the influence of adaptive and non-adaptive failure detectors over the execution of consensus algorithmsMestradoCiência da ComputaçãoMestre em Ciência da Computaçã

Scheduling and locking in multiprocessor real-time operating systems

With the widespread adoption of multicore architectures, multiprocessors are now a standard deployment platform for (soft) real-time applications. This dissertation addresses two questions fundamental to the design of multicore-ready real-time operating systems: (1) Which scheduling policies offer the greatest flexibility in satisfying temporal constraints; and (2) which locking algorithms should be used to avoid unpredictable delays? With regard to Question 1, LITMUSRT, a real-time extension of the Linux kernel, is presented and its design is discussed in detail. Notably, LITMUSRT implements link-based scheduling, a novel approach to controlling blocking due to non-preemptive sections. Each implemented scheduler (22 configurations in total) is evaluated under consideration of overheads on a 24-core Intel Xeon platform. The experiments show that partitioned earliest-deadline first (EDF) scheduling is generally preferable in a hard real-time setting, whereas global and clustered EDF scheduling are effective in a soft real-time setting. With regard to Question 2, real-time locking protocols are required to ensure that the maximum delay due to priority inversion can be bounded a priori. Several spinlock- and semaphore-based multiprocessor real-time locking protocols for mutual exclusion (mutex), reader-writer (RW) exclusion, and k-exclusion are proposed and analyzed. A new category of RW locks suited to worst-case analysis, termed phase-fair locks, is proposed and three efficient phase-fair spinlock implementations are provided (one with few atomic operations, one with low space requirements, and one with constant RMR complexity). Maximum priority-inversion blocking is proposed as a natural complexity measure for semaphore protocols. It is shown that there are two classes of schedulability analysis, namely suspension-oblivious and suspension-aware analysis, that yield two different lower bounds on blocking. Five asymptotically optimal locking protocols are designed and analyzed: a family of mutex, RW, and k-exclusion protocols for global, partitioned, and clustered scheduling that are asymptotically optimal in the suspension-oblivious case, and a mutex protocol for partitioned scheduling that is asymptotically optimal in the suspension-aware case. A LITMUSRT-based empirical evaluation is presented that shows these protocols to be practical

Dpcp (discard Past Consider Present) - A Novel Approach To Adaptive Fault Detection In Distributed Systems

Fault detection is a fundamental issue for fault tolerance in distributed systems. This paper presents the DPCP (Discard Past Consider Present) approach, that discards the last elapsed times of fault detection messages and considers only the current one. By this way, DPCP allows to perform a fast, accurated and scalable adaptive fault monitoring for asynchronous distributed systems. The scalability comes from the parameter Minimum-TimeUnit, that controls the minimum frequency of the fault monitoring messages. The fastness and accuracy of fault monitoring come from the changing of timeout and monitoring interval values as soon as the system workload and the Minimum TimeUnit allow. Some DPCP experiments on ACE+TAO were made to observe DPCP behavior on changing network workloads.7682Aguilera, M.K., Chen, W., Toueg, S., (1998) Failure Detection and Consensus in the Crash-Recovery Model, , Technical Report 98-1676, Department of Computer Science, Cornell UniversityChandra, T.D., Toueg, S., Unreliable failure detectors for reliable distributed systems (1996) Journal of the ACM, 43 (2), pp. 225-267Felber, P., (1998) The CORBA Object Group Service: A Service Approach to Object Groups in CORBA, , PhD thesis, École Polytechnique Fédérale de LausanneMacêdo, R.J.A., Failure detection in asynchronous distributed systems II Test and Fault Tolerance Workshop (II WTF 2000). Curitiba, Brazil, Jul. 2000, , http://www.lasid.ufba.br/public/artigos/Narasimhan, P., Moser, L.E., Melliar-Smith, P.M., Replica consistency of CORBA objects in partitionable distributed systems (1997) Distributed Systems Engineering, 4, pp. 139-150Natarajan, B., Gokhale, A., Schmidt, D.C., DOORS: Towards high-performance fault-tolerant CORBA Proceedings of the 2nd International Symposium on Distributed Objects and Applications (DOA '00). Antwerp, Belgium, Sept. 2000, OMG(2000) Fault Tolerant CORBA Specification, , Object Management GroupAprSchmidt, D.C., Douglas C. Schmidt's Welcome Page, , http://newport.ece.uci.edu/~schmidt/Sergent, N., Défago, X., Schiper, A., Failure detectors: Implementation issues and impact on consensus performance (1999), Technical Report SSC/1999/019. École Polytechnique Fédérale de LausanneSotoma, I., Madeira, E.R.M., ADAPTATION - Algorithms to ADAPTive FAulT MonItOriNg and their implementation on CORBA Proceedings IEEE of the 3rd International Symposium on Distributed Objects and Applications (DOA'01). Rome, Italy, Sep. 2001, , (accepted for publication

Fundamentals

Volume 1 establishes the foundations of this new field. It goes through all the steps from data collection, their summary and clustering, to different aspects of resource-aware learning, i.e., hardware, memory, energy, and communication awareness. Machine learning methods are inspected with respect to resource requirements and how to enhance scalability on diverse computing architectures ranging from embedded systems to large computing clusters

Fundamentals

Volume 1 establishes the foundations of this new field. It goes through all the steps from data collection, their summary and clustering, to different aspects of resource-aware learning, i.e., hardware, memory, energy, and communication awareness. Machine learning methods are inspected with respect to resource requirements and how to enhance scalability on diverse computing architectures ranging from embedded systems to large computing clusters

Real-Time Scheduling for GPUs with Applications in Advanced Automotive Systems

Self-driving cars, once constrained to closed test tracks, are beginning to drive alongside human drivers on public roads. Loss of life or property may result if the computing systems of automated vehicles fail to respond to events at the right moment. We call such systems that must satisfy precise timing constraints “real-time systems.” Since the 1960s, researchers have developed algorithms and analytical techniques used in the development of real-time systems; however, this body of knowledge primarily applies to traditional CPU-based platforms. Unfortunately, traditional platforms cannot meet the computational requirements of self-driving cars without exceeding the power and cost constraints of commercially viable vehicles. We argue that modern graphics processing units, or GPUs, represent a feasible alternative, but new algorithms and analytical techniques must be developed in order to integrate these uniquely constrained processors into a real-time system. The goal of the research presented in this dissertation is to discover and remedy the issues that prevent the use of GPUs in real-time systems. To overcome these issues, we design and implement a real-time multi-GPU scheduler, called GPUSync. GPUSync tightly controls access to a GPU’s computational and DMA processors, enabling simultaneous use despite potential limitations in GPU hardware. GPUSync enables tasks to migrate among GPUs, allowing new classes of real-time multi-GPU computing platforms. GPUSync employs heuristics to guide scheduling decisions to improve system efficiency without risking violations in real-time constraints. GPUSync may be paired with a wide variety of common real-time CPU schedulers. GPUSync supports closed-source GPU runtimes and drivers without loss in functionality. We evaluate GPUSync with both analytical and runtime experiments. In our analytical experiments, we model and evaluate over fifty configurations of GPUSync. We determine which configurations support the greatest computational capacity while maintaining real-time constraints. In our runtime experiments, we execute computer vision programs similar to those found in automated vehicles, with and without GPUSync. Our results demonstrate that GPUSync greatly reduces jitter in video processing. Research into real-time systems with GPUs is a new area of study. Although there is prior work on such systems, no other GPU scheduling framework is as comprehensive and flexible as GPUSync.Doctor of Philosoph

Quality of Service and Optimization in Data Integration Systems

This work presents techniques for the construction of a global data integrations system. Similar to distributed databases this system allows declarative queries in order to express user-specific information needs. Scalability towards global data integration systems and openness were major design goals for the architecture and techniques developed in this work. It is shown how service composition, extensibility and quality of service can be supported in an open system of providers for data, functionality for query processing operations, and computing power.Diese Arbeit präsentiert Techniken für den Aufbau eines globalen Datenintegrationssystems. Analog zu verteilten Datenbanken unterstützt dieses System deklarative Anfragen, mit denen Benutzer die gesuchte Information beschreiben können. Die Skalierbarkeit in einem globalen Kontext und die Offenheit waren hauptsächliche Entwicklungsziele der Architektur und der Techniken, die in dieser Arbeit entstanden sind. Es wird gezeigt wie Dienstekomposition, Erweiterbarkeit und Dienstgüte in einem offenen System von Anbietern für Daten, Anfrageverarbeitungsfunktionalität und Rechenleistung unterstützt werden können

Uses and Misuses of Chemicals in the British Home, 1930s – 1980s

Between the 1930s and 1980s, British home life was transformed by the adoption of labour-saving technologies, among which were chemicals. The voluntary, domestic use of man-made, branded and unbranded chemicals and products (excluding drugs or medicines) is a topic that has been neglected, making this thesis original. From my experience as a museum professional, I was aware that domestically used chemicals were collected but were rarely foregrounded or fully interpreted. This thesis has been constructed by piecing together details from objects, adverts, periodicals and specialist advice literature, as well as industry reports, oral histories and written testimonies. Three different user groups, each with their own distinct aims for using chemicals in the home are considered – housewives, gardeners and photographers – in addition to a group of unintended users, children. This selection of activities not only incorporated housework and leisure, but it also facilitated the study and comparison of women, men and children, which contributed to an inclusive view of domestic life and what it meant to be a domestic user of chemicals. Users and misusers are central to understanding why chemical products exist in particular forms. The types of problems – accidental ingestion, deliberate poisoning, explosions and allergic reactions – were consistent over the period studied. For the bodies responsible for the development, sale and use of chemicals, the tension between providing information so that users could behave safely, and withholding it so that they would either not be deterred from using chemicals or be tempted subvert any warnings, remained a continual preoccupation. The users and misusers in this narrative are given agency: they managed risks themselves, and sometimes they circumvented the safeguards that had been demanded on their behalf. This thesis argues that the domestic uses and misuses of ordinary chemicals shaped the chemicals that were ultimately available to use in British homes

Discuss And Fuse: Considering Modularity, Genericness, And Adaptation In The Development Of Consensus And Fault Detection Services

Although fault tolerant systems are badly needed, their development is not a trivial task. Considering fault tolerant distributed systems, this difficulty is even bigger, and any artifact that could make this task easier becomes highly valuable. In this paper, we propose and model a distributed consensus service and a fault detection service, namely, DisCusS and FuSe, that can be used as building blocks in the development of distributed fault tolerant applications. We also show the compliance of FuSe to FT-CORBA fault detection, and give some insights on the use of the proposed consensus service in a possible FT-CORBA implementation. 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