The effect of workload dependence in systems: Experimental evaluation, analytic models, and policy development

This dissertation presents an analysis of performance effects of burstiness (formalized by the autocorrelation function) in multi-tiered systems via a 3-pronged approach, i.e., experimental measurements, analytic models, and policy development. This analysis considers (a) systems with finite buffers (e.g., systems with admission control that effectively operate as closed systems) and (b) systems with infinite buffers (i.e., systems that operate as open systems).;For multi-tiered systems with a finite buffer size, experimental measurements show that if autocorrelation exists in any of the tiers in a multi-tiered system, then autocorrelation propagates to all tiers of the system. The presence of autocorrelated flows in all tiers significantly degrades performance. Workload characterization in a real experimental environment driven by the TPC-W benchmark confirms the existence of autocorrelated flows, which originate from the autocorrelated service process of one of the tiers. A simple model is devised that captures the observed behavior. The model is in excellent agreement with experimental measurements and captures the propagation of autocorrelation in the multi-tiered system as well as the resulting performance trends.;For systems with an infinite buffer size, this study focuses on analytic models by proposing and comparing two families of approximations for the departure process of a BMAP/MAP/1 queue that admits batch correlated flows, and whose service time process may be autocorrelated. One approximation is based on the ETAQA methodology for the solution of M/G/1-type processes and the other arises from lumpability rules. Formal proofs are provided: both approximations preserve the marginal distribution of the inter-departure times and their initial correlation structures.;This dissertation also demonstrates how the knowledge of autocorrelation can be used to effectively improve system performance, D_EQAL, a new load balancing policy for clusters with dependent arrivals is proposed. D_EQAL separates jobs to servers according to their sizes as traditional load balancing policies do, but this separation is biased by the effort to reduce performance loss due to autocorrelation in the streams of jobs that are directed to each server. as a result of this, not all servers are equally utilized (i.e., the load in the system becomes unbalanced) but performance benefits of this load unbalancing are significant

The Greater Boston Housing Report Card 2008: From Paradigm to Paradox: Understanding Greater Boston's New Housing Market

Combines an annual survey of Greater Boston's market conditions, housing production, rents, home prices, and public spending and support with an analysis of the dynamics of rising foreclosures, falling prices, and the unresolved problem of affordability

Integração comercial em uma estrutura de produção verticalmente fragmentada : teoria, métricas e efeitos

Orientadores: Fernando Sarti, Carolina Troncoso BaltarTese (doutorado) - Universidade Estadual de Campinas, Instituto de EconomiaResumo: A fragmentação vertical da produção mudou a capacidade de analisar os padrões de especialização dos países, bem como a relação entre comércio e crescimento econômico, revelando a necessidade de usar métricas que incorporem o surgimento de cadeias globais e regionais de valor. Esta pesquisa teve como objetivo investigar os aspectos conceituais e metodológicos da integração comercial no contexto da produção verticalmente fragmentada e do surgimento de cadeias globais e regionais de valor, avaliar os diferentes padrões de especialização, bem como compreender as mudanças na capacidade de resposta do comércio às variações de renda na atual fase da globalização. Para cumprir nossos propósitos, esta pesquisa está dividida em três seções principais. Na primeira seção, apresentamos alguns dos conceitos-chave da teorização das cadeias globais de valor (CGVs), enfatizando os conceitos e métricas de upgrading econômico e social para analisar mais detalhadamente os diferentes resultados da participação nas CGVs e então contribuir para a organização de um aparato teórico formal no contexto da literatura CGV. Argumentamos que as CGVs se tornaram um quadro explicativo prático e útil para entender como as empresas e os países estão envolvidos no processo de criação, distribuição e captura de valor. A segunda seção quantificou o envolvimento de um país nas CGVs de 1995 a 2011, bem como a dinâmica comercial regional de compartilhamento da produção global, usando métricas de comércio de valor adicionado construídas a partir de tabelas insumo-produto internacionais. Apresentamos um conjunto de fatos estilizados para ilustrar a importância da abordagem de valor-adicionado para a compreensão do comércio e produção globais. Além disso, nossas contribuições para a literatura sobre a geografia das cadeias globais de valor e sua regionalização estão centradas na análise do padrão de participação da América do Sul nas cadeias de valor em comparação a outros blocos regionais, bem como na criação de uma medida de hubness em termos de valor-adicionado. A terceira seção procurou analisar um dos efeitos multidimensionais do envolvimento dos países nas CGVs, investigando a relação entre participação nas CGVs e crescimento econômico. Em particular, nosso exercício empírico baseou-se em um modelo dinâmico de correção de erros para investigar a dinâmica de curto e longo prazo da relação entre importações e crescimento econômico para uma ampla amostra de economias avançadas e países em desenvolvimento e emergentes. Essa questão recebeu uma atenção renovada dada a lenta performance do comércio mundial nos últimos anos. Em resumo, a mudança da relação comércio-renda colocou alguns desafios que podem ter consequências para a dinâmica de crescimento econômico de longo prazo em todos os países, sendo ainda mais importante para economias em desenvolvimento e emergentes e, em última instância, podem transformar a ideia de que a integração comercial pode promover crescimento econômico em uma falácia. Portanto, essa pesquisa reforçou a necessidade de utilizar ferramentas de medição que englobem a realidade econômica cada vez mais complexa das cadeias globais e regionais de valor e possam orientar respostas políticas estratégicas para que a integração comercial assegure benefícios econômicos e crescimento econômico sustentadoAbstract: The vertically fragmentation of production has changed our ability to analyze countries¿ patterns of specialization, as well as the relationship between trade and economic growth, revealing the need for using metrics that incorporate the emergence of global and regional value chains. This research aimed to investigate the conceptual and methodological aspects of trade integration in the context of vertically fragmented production and emergence of global and regional value chains, to evaluate different patterns of specialization, as well as to understand how trade¿s responsiveness to income has changed at the current phase of globalization. For our purposes, this research is divided into three main sections. In the first section, we presented some of the key concepts in global value chains (GVCs) theorization, emphasizing the concepts and measures of economic and social upgrading, to further examine the manifold outputs from participation in GVCs and to contribute to the organization of a formal theoretical apparatus within the GVC literature. We argued that GVC has become a practical and useful explanatory framework for understanding how firms and countries are engaged in the process of value creation, distribution and capture. The second section has quantified a country's engagement in GVCs from 1995 to 2011, as well as the regional trade dynamics of global production sharing, using value-added trade metrics built from international input-output tables. We presented a set of stylized facts to illustrate the importance of the value-added framework to our understanding of global trade and production. Further, our contributions to the literature on the geography of global value chains and its regionalization are centered on the analysis of the pattern of participation of South America in value chains compared to other regional blocs, as well as on the creation of a hubness measure in value-added terms. The third section seeks to analyze one of the multidimensional effects of countries¿ engagement in GVCs, investigating the relation between countries¿ participation in GVCs and economic growth. In particular, our empirical exercise was based on a dynamic error correction model to examine the short-run and long-run dynamics of the import-income relationship for a broad sample of advanced economies and developing and emerging countries. This issue has received renewed attention given the sluggish performance of world trade in recent years. In summary, the changing trade-income relationship has posed some challenges that may have consequences for the long-term economic growth dynamics across countries, being even more important for developing and emerging economies, and ultimately can transform the idea that trade integration can promote economic growth into a fallacy. Therefore, we have reinforced the need for measurement tools that encompasses the increasingly complex economic reality within global and regional value chains and can guide strategic policy responses for trade integration to ensure economy-wide benefits and sustained economic growthDoutoradoTeoria EconomicaDoutora em Ciências EconômicasCAPE

Scheduling for today’s computer systems: bridging theory and practice

Scheduling is a fundamental technique for improving performance in computer systems. From web servers to routers to operating systems, how the bottleneck device is scheduled has an enormous impact on the performance of the system as a whole. Given the immense literature studying scheduling, it is easy to think that we already understand enough about scheduling. But, modern computer system designs have highlighted a number of disconnects between traditional analytic results and the needs of system designers. In particular, the idealized policies, metrics, and models used by analytic researchers do not match the policies, metrics, and scenarios that appear in real systems. The goal of this thesis is to take a step towards modernizing the theory of scheduling in order to provide results that apply to today’s computer systems, and thus ease the burden on system designers. To accomplish this goal, we provide new results that help to bridge each of the disconnects mentioned above. We will move beyond the study of idealized policies by introducing a new analytic framework where the focus is on scheduling heuristics and techniques rather than individual policies. By moving beyond the study of individual policies, our results apply to the complex hybrid policies that are often used in practice. For example, our results enable designers to understand how the policies that favor small job sizes are affected by the fact that real systems only have estimates of job sizes. In addition, we move beyond the study of mean response time and provide results characterizing the distribution of response time and the fairness of scheduling policies. These results allow us to understand how scheduling affects QoS guarantees and whether favoring small job sizes results in large job sizes being treated unfairly. Finally, we move beyond the simplified models traditionally used in scheduling research and provide results characterizing the effectiveness of scheduling in multiserver systems and when users are interactive. These results allow us to answer questions about the how to design multiserver systems and how to choose a workload generator when evaluating new scheduling designs