Event Stream Processing with Multiple Threads

Current runtime verification tools seldom make use of multi-threading to speed up the evaluation of a property on a large event trace. In this paper, we present an extension to the BeepBeep 3 event stream engine that allows the use of multiple threads during the evaluation of a query. Various parallelization strategies are presented and described on simple examples. The implementation of these strategies is then evaluated empirically on a sample of problems. Compared to the previous, single-threaded version of the BeepBeep engine, the allocation of just a few threads to specific portions of a query provides dramatic improvement in terms of running time

Mage: Online Interference-Aware Scheduling in Multi-Scale Heterogeneous Systems

Heterogeneity has grown in popularity both at the core and server level as a way to improve both performance and energy efficiency. However, despite these benefits, scheduling applications in heterogeneous machines remains challenging. Additionally, when these heterogeneous resources accommodate multiple applications to increase utilization, resources are prone to contention, destructive interference, and unpredictable performance. Existing solutions examine heterogeneity either across or within a server, leading to missed performance and efficiency opportunities. We present Mage, a practical interference-aware runtime that optimizes performance and efficiency in systems with intra- and inter-server heterogeneity. Mage leverages fast and online data mining to quickly explore the space of application placements, and determine the one that minimizes destructive interference between co-resident applications. Mage continuously monitors the performance of active applications, and, upon detecting QoS violations, it determines whether alternative placements would prove more beneficial, taking into account any overheads from migration. Across 350 application mixes on a heterogeneous CMP, Mage improves performance by 38% and up to 2x compared to a greedy scheduler. Across 160 mixes on a heterogeneous cluster, Mage improves performance by 30% on average and up to 52% over the greedy scheduler, and by 11% over the combination of Paragon [15] for inter- and intra-server heterogeneity

Understanding user experience of mobile video: Framework, measurement, and optimization

Since users have become the focus of product/service design in last decade, the term User eXperience (UX) has been frequently used in the field of Human-Computer-Interaction (HCI). Research on UX facilitates a better understanding of the various aspects of the user’s interaction with the product or service. Mobile video, as a new and promising service and research field, has attracted great attention. Due to the significance of UX in the success of mobile video (Jordan, 2002), many researchers have centered on this area, examining users’ expectations, motivations, requirements, and usage context. As a result, many influencing factors have been explored (Buchinger, Kriglstein, Brandt & Hlavacs, 2011; Buchinger, Kriglstein & Hlavacs, 2009). However, a general framework for specific mobile video service is lacking for structuring such a great number of factors. To measure user experience of multimedia services such as mobile video, quality of experience (QoE) has recently become a prominent concept. In contrast to the traditionally used concept quality of service (QoS), QoE not only involves objectively measuring the delivered service but also takes into account user’s needs and desires when using the service, emphasizing the user’s overall acceptability on the service. Many QoE metrics are able to estimate the user perceived quality or acceptability of mobile video, but may be not enough accurate for the overall UX prediction due to the complexity of UX. Only a few frameworks of QoE have addressed more aspects of UX for mobile multimedia applications but need be transformed into practical measures. The challenge of optimizing UX remains adaptations to the resource constrains (e.g., network conditions, mobile device capabilities, and heterogeneous usage contexts) as well as meeting complicated user requirements (e.g., usage purposes and personal preferences). In this chapter, we investigate the existing important UX frameworks, compare their similarities and discuss some important features that fit in the mobile video service. Based on the previous research, we propose a simple UX framework for mobile video application by mapping a variety of influencing factors of UX upon a typical mobile video delivery system. Each component and its factors are explored with comprehensive literature reviews. The proposed framework may benefit in user-centred design of mobile video through taking a complete consideration of UX influences and in improvement of mobile videoservice quality by adjusting the values of certain factors to produce a positive user experience. It may also facilitate relative research in the way of locating important issues to study, clarifying research scopes, and setting up proper study procedures. We then review a great deal of research on UX measurement, including QoE metrics and QoE frameworks of mobile multimedia. Finally, we discuss how to achieve an optimal quality of user experience by focusing on the issues of various aspects of UX of mobile video. In the conclusion, we suggest some open issues for future study

End-to-End Application Cloning for Distributed Cloud Microservices with Ditto

We present Ditto, an automated framework for cloning end-to-end cloud applications, both monolithic and microservices, which captures I/O and network activity, as well as kernel operations, in addition to application logic. Ditto takes a hierarchical approach to application cloning, starting with capturing the dependency graph across distributed services, to recreating each tier's control/data flow, and finally generating system calls and assembly that mimics the individual applications. Ditto does not reveal the logic of the original application, facilitating publicly sharing clones of production services with hardware vendors, cloud providers, and the research community. We show that across a diverse set of single- and multi-tier applications, Ditto accurately captures their CPU and memory characteristics as well as their high-level performance metrics, is portable across platforms, and facilitates a wide range of system studies

Deterministic Parallel Hypergraph Partitioning

Balanced hypergraph partitioning is a classical NP-hard optimization problem with applications in various domains such as VLSI design, simulating quantum circuits, optimizing data placement in distributed databases or minimizing communication volume in high-performance computing. Engineering parallel heuristics for this problem is a topic of recent research. Most of them are non-deterministic though. In this work, we design and implement a highly scalable deterministic algorithm in the state-of-the-art parallel partitioning framework Mt-KaHyPar. On our extensive set of benchmark instances, it achieves similar partition quality and performance as a comparable but non-deterministic configuration of Mt-KaHyPar and outperforms the only other existing parallel deterministic algorithm BiPart regarding partition quality, running time and parallel speedups

LUTS : a Light-Weight User-Level Transaction Scheduler

Orientador: Guido Costa Souza de AraújoTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Sistemas de Memória Transacional em Software (MTS) têm sido usados como uma abordagem para melhorar o desempenho ao permitir a execução concorrente de blocos atômicos. Porém, em cenários com alta contenção, sistemas baseados em MTS podem diminuir o desempenho consideravelmente, já que a taxa de conflitos aumenta. Políticas de gerenciamento de contenção têm sido usadas como uma forma de selecionar qual transação abortar quando um conflito ocorre. No geral, gerenciadores de contenção não são capazes de evitar conflitos, tendo em vista que eles apenas selecionam qual transação abortar e o momento em que ela deve reiniciar. Como gerenciadores de contenção agem somente após a detecção de um conflito, é difícil aumentar a taxa de transações finalizadas com sucesso. Abordagens mais pró-ativas foram propostas, focando na previsão de quando uma transação deve abortar e atrasando o início de sua execução. Contudo, as técnicas pró-ativas continuam sendo limitadas, já que elas não substituem a transação fadada a abortar por outra transação com melhores probabilidades de sucesso, ou quando o fazem, dependem do sistema operacional para essa tarefa, tendo pouco ou nenhum controle de qual transação será a substituta. Esta tese apresenta o LUTS, Lightweight User-Level Transaction Scheduler, um escalonador de transação de baixo custo em nível de usuário. Diferente de outras técnicas, LUTS provê maneiras de selecionar outra transação a ser executada em paralelo, melhorando o desempenho do sistema. Nós discutimos o projeto do LUTS e propomos uma heurística dinâmica, com o objetivo de evitar conflitos, que foi construída utilizando os métodos disponibilizados pelo LUTS. Resultados experimentais, conduzidos com os conjuntos de aplicações STAMP e STMBench7, e executando nas bibliotecas TinySTM e SwissTM, mostram como nossa heurística para evitar conflitos pode melhorar efetivamente o desempenho de sistema de MTS em aplicações com alta contençãoAbstract: Software Transaction Memory (STM) systems have been used as an approach to improve performance, by allowing the concurrent execution of atomic blocks. However, under high-contention workloads, STM-based systems can considerably degrade performance, as transaction conflict rate increases. Contention management policies have been used as a way to select which transaction to abort when a conflict occurs. In general, contention managers are not capable of avoiding conflicts, as they can only select which transaction to abort and the moment it should restart. Since contention manager's act only after a conflict is detected, it becomes harder to effectively increase transaction throughput. More proactive approaches have emerged, aiming at predicting when a transaction is likely to abort, postponing its execution. Nevertheless, most of the proposed proactive techniques are limited, as they do not replace the doomed transaction by another or, when they do, they rely on the operating system for that, having little or no control on which transaction to run. This article proposes LUTS, a Lightweight User-Level Transaction Scheduler. Unlike other techniques, LUTS provides the means for selecting another transaction to run in parallel, thus improving system throughput. We discuss LUTS design and propose a dynamic conflict-avoidance heuristic built around its scheduling capabilities. Experimental results, conducted with the STAMP and STMBench7 benchmark suites, running on TinySTM and SwissTM, show how our conflict-avoidance heuristic can effectively improve STM performance on high contention applicationsDoutoradoCiência da ComputaçãoDoutor em Ciência da Computaçã

Parallel architectures and runtime systems co-design for task-based programming models

The increasing parallelism levels in modern computing systems has extolled the need for a holistic vision when designing multiprocessor architectures taking in account the needs of the programming models and applications. Nowadays, system design consists of several layers on top of each other from the architecture up to the application software. Although this design allows to do a separation of concerns where it is possible to independently change layers due to a well-known interface between them, it is hampering future systems design as the Law of Moore reaches to an end. Current performance improvements on computer architecture are driven by the shrinkage of the transistor channel width, allowing faster and more power efficient chips to be made. However, technology is reaching physical limitations were the transistor size will not be able to be reduced furthermore and requires a change of paradigm in systems design. This thesis proposes to break this layered design, and advocates for a system where the architecture and the programming model runtime system are able to exchange information towards a common goal, improve performance and reduce power consumption. By making the architecture aware of runtime information such as a Task Dependency Graph (TDG) in the case of dataflow task-based programming models, it is possible to improve power consumption by exploiting the critical path of the graph. Moreover, the architecture can provide hardware support to create such a graph in order to reduce the runtime overheads and making possible the execution of fine-grained tasks to increase the available parallelism. Finally, the current status of inter-node communication primitives can be exposed to the runtime system in order to perform a more efficient communication scheduling, and also creates new opportunities of computation and communication overlap that were not possible before. An evaluation of the proposals introduced in this thesis is provided and a methodology to simulate and characterize the application behavior is also presented.El aumento del paralelismo proporcionado por los sistemas de cómputo modernos ha provocado la necesidad de una visión holística en el diseño de arquitecturas multiprocesador que tome en cuenta las necesidades de los modelos de programación y las aplicaciones. Hoy en día el diseño de los computadores consiste en diferentes capas de abstracción con una interfaz bien definida entre ellas. Las limitaciones de esta aproximación junto con el fin de la ley de Moore limitan el potencial de los futuros computadores. La mayoría de las mejoras actuales en el diseño de los computadores provienen fundamentalmente de la reducción del tamaño del canal del transistor, lo cual permite chips más rápidos y con un consumo eficiente sin apenas cambios fundamentales en el diseño de la arquitectura. Sin embargo, la tecnología actual está alcanzando limitaciones físicas donde no será posible reducir el tamaño de los transistores motivando así un cambio de paradigma en la construcción de los computadores. Esta tesis propone romper este diseño en capas y abogar por un sistema donde la arquitectura y el sistema de tiempo de ejecución del modelo de programación sean capaces de intercambiar información para alcanzar una meta común: La mejora del rendimiento y la reducción del consumo energético. Haciendo que la arquitectura sea consciente de la información disponible en el modelo de programación, como puede ser el grafo de dependencias entre tareas en los modelos de programación dataflow, es posible reducir el consumo energético explotando el camino critico del grafo. Además, la arquitectura puede proveer de soporte hardware para crear este grafo con el objetivo de reducir el overhead de construir este grado cuando la granularidad de las tareas es demasiado fina. Finalmente, el estado de las comunicaciones entre nodos puede ser expuesto al sistema de tiempo de ejecución para realizar una mejor planificación de las comunicaciones y creando nuevas oportunidades de solapamiento entre cómputo y comunicación que no eran posibles anteriormente. Esta tesis aporta una evaluación de todas estas propuestas, así como una metodología para simular y caracterizar el comportamiento de las aplicacionesPostprint (published version