LUTS: A lightweight user-level transaction scheduler

Software Transactional Memory (STM) systems have poor performance under high contention scenarios. Since many transactions compete for the same data, most of them are aborted, wasting processor runtime. Contention management policies are typically used to avoid that, but they are passive approaches as they wait for an abort to happen so they can take action. More proactive approaches have emerged, trying to predict when a transaction is likely to abort so its execution can be delayed. Such 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 should run. In this paper we propose LUTS, a Lightweight User-Level Transaction Scheduler, which is based on an execution context record mechanism. Unlike other techniques, LUTS provides the means for selecting another transaction to run in parallel, thus improving system throughput. Moreover, it avoids most of the issues caused by pseudo parallelism, as it only launches as many system-level threads as the number of available processor cores. We discuss LUTS design and present three conflict-avoidance heuristics built around LUTS scheduling capabilities. Experimental results, conducted with STMBench7 and STAMP benchmark suites, show LUTS efficiency when running high contention applications and how conflict-avoidance heuristics can improve STM performance even more. In fact, our transaction scheduling techniques are capable of improving program performance even in overloaded scenarios. © 2011 Springer-Verlag.

Transaction scheduling using dynamic conflict avoidance

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 managers 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 applications. © 2012 Springer Science+Business Media, LLC.

Fuzzy rule-based system for evaluation of uncertainty transaction in cassava chain

A fuzzy ruled-based system was developed in this study and resulted in an index indicating the level of uncertainty related to commercial transactions between cassava growers and their dealers. The fuzzy system was developed based on Transaction Cost Economics approach. The fuzzy system was developed from input variables regarding information sharing between grower and dealer on “Demand/purchase Forecasting”, “Production Forecasting” and “Production Innovation”. The output variable is the level of uncertainty regarding the transaction between seller and buyer agent, which may serve as a system for detecting inefficiencies. Evidences from 27 cassava growers registered in the Regional Development Offices of Tupa and Assis, São Paulo, Brazil, and 48 of their dealers supported the development of the system. The mathematical model indicated that 55% of the growers present a Very High level of uncertainty, 33% present Medium or High. The others present Low or Very Low level of uncertainty. From the model, simulations of external interferences can be implemented in order to improve the degree of uncertainty and, thus, lower transaction costs.

Análise da comercialização de energia elétrica cogerada pelo setor sucroalcooleiro no estado de São Paulo

O Brasil viveu, em 2001, uma crise de oferta de energia elétrica sem precedentes que coincidiu com o processo de reestruturação do setor elétrico brasileiro e possibilitou aos autoprodutores de energia elétrica,como o setor sucroalcooleiro, comercializarem o excedente de energia, obtidos pelo processo de cogeração, que apesar do elevado potencial de comercialização, não está sendo devidamente aproveitado. Este trabalho teve por objetivo caracterizar o mercado de energia elétrica cogerada e analisar os obstáculos à comercialização da energia cogerada, à luz da existência dos custos de transação e econômicos, enfrentados pelo setor sucroalcooleiro e distribuidoras. Para a coleta de informações, foram realizadas entrevistas semi-estruturadas com o responsável pela área de cogeração das usinas e distribuidora de energia, que consistiam em perguntas pré-determinadas que foram lidas na mesma ordem e da mesma maneira para todos os entrevistados para assegurar a comparabilidade dos resultados. As entrevistas foram gravadas, transcritas e examinadas por meio da análise de conteúdo. Os resultados indicaram que poderiam ser estabelecidos contratos de longo prazo, mas os custos de transação e econômicos entre os agentes podem estar superando os benefícios da comercialização de energia elétrica cogerada, fazendo os agentes atuarem preferencialmente no mercado spot

Fragmentos de um modelo: pequenas lavouras de café e acumulação de capitais. Franca/São Paulo 1890-1914

Este artigo versa sobre a importância da pequena cafeicultura no complexo cafeeiro entre 1890 e 1914. Discutimos aqui as relações de trabalho, as formas de financiamento e o modo como a pequena propriedade se insere neste universo. Utilizamos como fontes prioritárias os contratos de trabalho que envolviam a formação e/ou o trato de cafeeiros e as escrituras de dívidas hipotecárias, ambas lavradas nos Livros Cartoriais, fontes estas ainda não trabalhadas pela historiografia de forma mais sistemática. Desviamos nosso olhar para uma região marcada predominantemente pelas pequenas e médias fazendas produtoras de café, observando a dinâmica da acumulação em um período de expansão e de crise da cafeicultura.

Formação, sustentação ou implosão de uma bolha imobiliária? A dinâmica de preços no mercado de imóveis de Natal no período 2005-2010

A motivação para a realização deste artigo foi a percepção de que o movimento de preços dos imóveis em Natal apresentava componentes que precisavam ser investigados, notadamente o influxo de capital estrangeiro, sobretudo para aplicação nos setores de turismo e imobiliário e o comportamento do crédito imobiliário. O objetivo do trabalho é examinar a evolução dos preços no mercado de imóveis da cidade no período 2005; 2010. Os indicadores levantados permitiram uma coleta de evidências suficiente para ampliar o grau de confiança nas hipóteses de que, de fato: a) ocorreu uma bolha no mercado de imóveis no triênio 2005; 2007; b) a bolha não implodiu no biênio 2009; 2010, após a crise financeira de 2008, pois o movimento de alta de preços se manteve tanto nos imóveis vendidos na planta quanto nos imóveis prontos.

Crédito e pequena cafeicultura no oeste paulista: Franca/SP 1890-1914

This article turns on the importance of the small coffee production in the coffee complex economy between 1890 and 1914. We argue here the relations of work, the forms of financing and the way as the small coffee production inserts itself in this universe. We use as priority sources the employment contracts that involved the formation and/or the treatment of coffee trees and the Writes of mortgage debts, both recorded in Notarial Books, documents not used by historiography in a systematical way. We turns our look for a region marked predominantly for small and the middle producing farms of coffee, observing the dynamics of the accumulation in a period of expansion and crisis of the coffee economy.

Análise da eficiência de dois sistemas de distribuição de rosas do Estado de São Paulo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A comercialização da energia elétrica cogerada pelo setor sucroalcooleiro em regiões do estado de São Paulo

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

O problema do financiamento: uma análise histórica sobre o crédito no complexo cafeeiro paulista. Casa Branca (1874-1914)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Produção, economicidade e parâmetros energéticos do cogumelo Agaricus blazei: um enfoque de cadeia produtiva

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

O assunto do e-mail como indício de fraude: contribuições da organização da informação para a prevenção criminal

Pós-graduação em Ciência da Informação - FFC

La crisis restructral del capitalismo y sus repercusiones

This article analyzes the structural crisis of capitalism that began when the speculative home mortgage bubble burst in the United States in 2007, and the repercussions of that phenome- non. The current crisis is the outcome of a series of processes unleashed as a result of the crisis of overaccumulation of capital in the 1970s, which generated, on the one hand, the conditions for financial capital’s dominance and, on the other, a new frontier for the accumulation of cap- ital in East Asia, especially in China. The crisis calls into question the centrality of the North American economy, but that does not necessarily mean the shift of capitalism’s hegemonic cen- ter to Asia. Here we will argue that we are headed toward a multipolar world.

O descumprimento da transação penal e suas consequencias à luz das finalidades de política criminal e da legitimação constitucional

Pós-graduação em Direito - FCHS

A crise do subprime e seus efeitos sobre os Estados Unidos e reflexos no Brasil

Between December 2007 and June 2009 the United States witnessed 18 months of recession that became known as the subprime crisis. Beginning in the housing market, the crisis moved into the banking and financial markets and spread throughout the entire economy through a domino effect, affecting the majority of other businesses. A major reflection of this was the large rise in unemployment rates due to business slashing jobs in an attempt to preserve cash. Although the crisis has officially ended, the unemployment rate reached over 10% in 2010 in the United States. American's continue to seek new jobs in a very difficult employment market, while attempting to manage the family household budget. American household income, which decreased either by pay cuts, job loss, and the effects of inflation, leads the majority of Americans to declare that the crisis had not yet ended. The crisis has spread to the world in varying degrees. Brazil was one of the countries least affected due to government policies and the large amount of foreign exchange. Although the crisis has affected Brazil only slightly, we will show how it reached this country and how the government solved this problem. This research paper will explain how the subprime crisis began, how it manifested itself in the U.S. economy and throughout the population. Also, it will show the crisis’ effects in Brazil and show some statements from Americans with their respective views and their experiences relative to the crisis