DVFS governor for HPC: Higher, Faster, Greener

International audienceIn High Performance Computing, being respectful of the environment is usually secondary compared to performance: The faster, the better. As Exascale computing is in the spotlight, electric power concerns arise as current exascale projects might need too much power to even boot. A recent incentive (Exascale at maximum 20MW) shows that reality is catching up with HPC center designers. Beyond classical works on hardware infrastructure or at the middleware level, we do believe that system-level solutions have great potential for energy reduction. Moreover energy-reduction has often been neglected by the HPC community that focus mainly on raw computing performance. In the literature, energy savings is achieved mainly by two means: Either processor load is the only metric taken into account to reduce processors frequency and to ensure no impact on raw performances, Or processor frequency is managed only at task level outside the critical path. In this article we show that designing and implementing a DVFS (Dynamic Voltage and Frequency Scaling) mechanism based on instantaneous system values (here network activity) can save up to 25% of energy consumption while reducing marginally performance. In several cases, reducing energy consumption also leads to an increase in performances because of the thermal budget of recent processors. This work is validated with real experiments on a Linux cluster using the NAS Parallel Benchmark (NPB)

Hidden spectral symmetries and mode stability of subextremal Kerr(-dS) black holes

We uncover hidden spectral symmetries of the Teukolsky equation in Kerr(-de Sitter) black holes, recently conjectured by Aminov, Grassi and Hatsuda (arXiv: 2006.06111 and arXiv: 2007.07906, 2020) in the zero cosmological constant case. Using these symmetries, we provide a new, simpler proof of mode stability for subextremal Kerr black holes. We also present a partial mode stability result for Kerr-de Sitter black holes.Comment: 24 pages, 1 figur

Energy aware clouds scheduling using anti-load balancing algorithm : EACAB

International audienceCloud computing is a highly scalable and cost-effective infrastructure for running HPC, enterprise and Web applications. However rapid growth of the demand for computational power by scientific, business and web- applications has led to the creation of large-scale data centers consuming enormous amounts of electrical power. Hence, energy-efficient solutions are required to minimize their energy consumption. The objective of our approach is to reduce data center’s total energy consumption by controlling cloud applications’ overall resource usage while guarantying service level agreement. This article presents Energy aware clouds scheduling using anti-load balancing algorithm (EACAB). The proposed algorithm works by associating a credit value with each node. The credit of a node depends on its affinity to its jobs, its current workload and its communication behavior. Energy savings are achieved by continuous consolidation of VMs according to current utilization of resources, virtual network topologies established between VMs and thermal state of computing nodes. The experiment results show that the cloud application energy consumption and energy efficiency is being improved effectively

Energy-efficient and thermal-aware resource management for heterogeneous datacenters

International audienceWe propose in this paper to study the energy-, thermal- and performance-aware resource management in heterogeneous datacenters. Witnessing the continuous development of heterogeneity in datacenters, we are confronted with their different behaviors in terms of performance, power consumption and thermal dissipation: indeed, heterogeneity at server level lies both in the computing infrastructure (computing power, electrical power consumption) and in the heat removal systems (different enclosure, fans, thermal sinks). Also the physical locations of the servers become important with heterogeneity since some servers can (over)heat others. While many studies address independently these parameters (most of the time performance and power or energy), we show in this paper the necessity to tackle all these aspects for an optimal resource management of the computing resources. This leads to improved energy usage in a heterogeneous datacenter including the cooling of the computer rooms. We build our approach on the concept of heat distribution matrix to handle the mutual influence of the servers, in heterogeneous environments, which is novel in this context. We propose a heuristic to solve the server placement problem and we design a generic greedy framework for the online scheduling problem. We derive several single-objective heuristics (for performance, energy, cooling) and a novel fuzzy-based priority mechanism to handle their tradeoffs. Finally, we show results using extensive simulations fed with actual measurements on heterogeneous servers

Valgreen: an Application's Energy Profiler

International audienceThe popularity of hand-held and portable devices put the energy aware computing in evidence. The need for long time batteries surpasses the hardware manufacturer, impacting the operational system policies and software development. Power modeling of applications has been studied during the last years and can be used to estimate their total energy. In order to aid the programmer to implement energy efficient algorithms, this paper introduces an application's energy profiler, namely Valgreen, which exploits the battery's information in order to generate an architecture independent power model through a calibration process

Energy Consumption Library

International audienceThe energy consumption of a computing system depends not only on its architecture, but also on its usage. This paper describes the Energy Consumption Library (libec), a modular library of sensors and power estimators, which do not depend on wattmeter to measure the power dissipated by a machine and/or the applications that it executes, etc. In addition, four use cases are used to demonstrate some of the library's capabilities

História dos trabalhadores negros no Brasil e desigualdade racial

O objetivo desse texto será articular alguns elementos que permitam uma compreensão, ainda que panorâmica, do sentido dos papéis que o trabalhador negro vem desempenhando no conjunto maior da história do trabalho no Brasil. Mais do que isso, o desenvolvimento de tal proposta viabilizará uma visada mais acurada da importância da inserção do negro no mercado de trabalho no Brasil pós-abolição, o papel central que ocupa a educação na possibilidade da alocação de melhores posições e postos de trabalho e emprego, além de uma participação mais ampla do negro no consumo de bens culturais e uma maior flexibilidade na estrutura de mobilidade social. Finalmente discute o papel dos marcos jurídicos na luta antidiscriminatória no mercado de trabalho no Brasil

Raça e gênero na saúde mental do Distrito Federal

O presente livro é resultado de pesquisa realizada com financiamento do CNPQ, cujo objetivo foi construir o perfil sócio-econômico e cultural da população manicomial atendida ou acolhida em duas das mais importantes instituições de saúde mental do Distrito Federal; O Instituto de Saúde mental (ISM) e o Hospital São Vicente de Paulo (HSVP). O volume apresenta, além do relatório de pesquisa produzido por mim, coordenador da pesquisa, também outros trabalhos cujo esforço foi pensar teoricamente, sobretudo, formulando problemas e refletindo sobre realidades que emergiram diretamente dos dados coletados, analisados e interpretados.UniCEU

25 anos da Constituição Federal de 1988: uma comemoração crítica

Há vinte e cinco anos promulgava-se então aquela que ficou conhecida como a Constituição mais democrática da vida republicana brasileira. Desde então muitas coisas mudaram, tanto no corpo original daquele documento quanto, mas, sobretudo, na sociedade brasileira de um modo geral. Os artigos reunidos nessa publicação celebram, cada um a seu modo, os vinte e cinco anos de existência da Constituição Federal de 1988. Se, divergem amplamente no que diz respeito à temática particular escolhida à abordagem teórica desenvolvida e às expectativas quanto ao potencial transformador da sociedade brasileira inscrito em suas páginas, convergem na medida em que, em sua maioria, apresentam uma fecunda perspectiva critica da Carta magna de 1988, avaliando, dimensionando os descaminhos e descompassos desta com os objetivos, anseios, demandas e reivindicações de diversos setores da sociedade brasileira.UniCEU