La gestion des ressources pour des infrastructures vertes par la reconfiguration

Cette HDR présente des travaux dans le contexte des systèmes informatiques à grande échelle pouvant être des grilles de calcul ou le cloud computing. Partant de deux constats : la consommation énergétique de ces systèmes est trop importante et ces systèmes sont de plus en complexes, ce mémoire se propose de répondre à la problématique suivante : comment gérer de manière optimale les ressources afin d'obtenir des infrastructures matérielles et logicielles "vertes" c'est à dire efficaces en énergie ? Ces travaux proposent trois axes de recherche : le premier en considérant le système complet et les leviers verts associés, le deuxième en étudiant des politiques d'allocation de ressources avec contraintes d'énergie et de chaleur, le troisième en étudiant des reconfigurations autonomiques d'applications. Pour finir, une description d'un centre de décision autonome pour des infrastructures vertes est proposée

Modelling Constrained Dynamic Software Architecture with Attributed Graph Rewriting Systems

Dynamic software architectures are studied for handling adap- tation in distributed systems, coping with new requirements, new envi- ronments, and failures. Graph rewriting systems have shown their ap- propriateness to model such architectures, particularly while considering the consistency of theirs reconfigurations. They provide generic formal means to specify structural properties, but imply a poor description of specific issues like behavioural properties. This paper lifts this limita- tion by proposing a formal approach for integrating the consideration of constraints, non-trivial attributes, and their propagation within the framework of graph rewriting systems

Correctness by Construction and Style Preserving Reconfigurations of Distributed Systems.

In distributed systems and dynamic environments, software architectures may evolve. A crucial issue when conducting system evolutions is to maintain the system in a consistent and functional state. Based on formal proofs in design-time, correctness by construction has recently emerged to efficiently guarantee system coherency. This article proposes a new method for the construction and specification of correct by construction system reconfigurations. Such transformations are characterized by graph rewriting rules that necessarily preserve the coherency of a system. We firstly propose operators on graph transformations and show that they conserve their correctness. Given a system specified by a graph grammar, these operators then serve to construct and characterize a set of correct transformations. We show in particular that any correct configuration can be reached starting from any other one without inconsistent intermediate step, using these transformations only

Fiscal competition in a transition economy

Endast sammandrag. Inbundna avhandlingar kan sökas i Helka-databasen (http://www.helsinki.fi/helka). Elektroniska kopior av avhandlingar finns antingen öppet på nätet eller endast tillgängliga i bibliotekets avhandlingsterminaler.Only abstract. Paper copies of master’s theses are listed in the Helka database (http://www.helsinki.fi/helka). Electronic copies of master’s theses are either available as open access or only on thesis terminals in the Helsinki University Library.Vain tiivistelmä. Sidottujen gradujen saatavuuden voit tarkistaa Helka-tietokannasta (http://www.helsinki.fi/helka). Digitaaliset gradut voivat olla luettavissa avoimesti verkossa tai rajoitetusti kirjaston opinnäytekioskeilla.The paper analyses effects of fiscal competition for mobile capital between identical regions in a transition economy. I add two features characteristic of transition economies into the familiar model of fiscal competition by Keen-Marchand (1997). Firstly, the economy is seen to consist of two sectors with differing productivities. Even though both sectors use same inputs, the new sector is more productive than the old one. Secondly, decision-makers are assumed to be only partially benevolent. They maximise a weighted average of consumer's utility and their private benefit that originates in the old sector production. The primary interest centers on the effects of fiscal competition on the overall level and on the composition of public goods provision when the economy is characterised by the above-mentioned transition features. Two specifications for decision-maker's private benefit will be used. The basic case corresponds closely to that in Keen-Marchand (1997) producing results largely in line with theirs. The level of public goods provision is proved to be too low in a competitive equilibrium. Additionally, the composition of public goods will be distorted towards too much infrastructure and too little social public good. A common increase in capital tax rates or a common change in the composition of public goods would unambigously increase consumer's welfare, but the welfare change is proven to be smaller than it would be in pure Keen-Marchand (1997) model. The alternative specification of decision-maker's private benefit may be seen as a special case of the one used in Qian-Roland (1998). As it is assumed that politicans own state sector rents, the results change radically. It is no longer self-evident that too little public goods is provided in a competitive equilibrium and a common policy change may, in fact, be welfare-deterioring for the consumers. Specifically, when the relative share of old sector production in a region is large, a common increase in tax on mobile capital may decrease consumer's welfare. The opposite is proven to hold if the production structure of the transition economy (i.e. the relative share of old sector production) is very close to a standard one-sector economy

Software architectures: multi-scale refinement

We propose a multi-scale modeling approach for complex software system architecture description. The multi-scale description may help to obtain meaningful granularities of these systems and to understand and master their complexity. This vision enables an architect designer to express constraints concerning different description levels, oriented to facilitate adaptability management. We define a correct-by-design approach that allows a given abstract architectural description to be refined into architecture models. We follow a progressive refinement process based on model transformations; it begins with a coarse-grain description and ends with a fine-grain description that specifies design details. The adaptability property management is performed through model transformation operations. The model transformation ensures the correctness of UML description, and the correctness of the modeled system. We experimented our approach with a use case that models a smart home system for the monitoring of elderly and disabled persons at home

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

Self-management of machine-to-machine communications: a multi-models approach

International audienceMachine-to-Machine (M2M) paradigm apply to systems composed by numerous devices sharing information and making cooperative decisions with little or no human intervention. The M2M standard defined by the European Telecommunications Standards Institute (ETSI) is the only one providing an end-to-end view of the global M2M architecture. Noticeably, it furnishes a standardised framework for inter-operable M2M services that satisfies most of M2M modelling requirements. However, and even though M2M systems usually operate in highly evolving contexts, this standard does not address the issue of system adaptations. It is furthermore unsuitable for building self-managed systems. This paper introduces a multi-model approach for modelling manageable M2M systems. Said approach consists in a formal graph-based model on top of the ETSI M2M standard, alongside bi-directional updates that ensure layer coherency. Its fitness for enforcing self-management properties is demonstrated by designing high-level reconfiguration rules. Finally, its applicability is illustrated and evaluated using a smart-metering application

Enhanced Graph Rewriting Systems for Complex Software Domains (SoSyM Abstract)

International audienceMethodologies for correct by construction reconfigu-rations can efficiently solve consistency issues in dynamic software architecture. Graph-based models are appropriate for designing such architectures and methods. At the same time, they may be unfit to characterize a system from a non functional perspective. This stems from efficiency and applicability limitations in handling time-varying characteristics and their related dependencies. In order to lift these restrictions, an extension to graph rewriting systems is proposed herein. The suitability of this approach, as well as the restraints of currently available ones, are illustrated, analysed and experimentally evaluated with reference to a concrete example. This investigation demonstrates that the conceived solution can: (i) express any kind of algebraic dependencies between evolving requirements and properties; (ii) significantly ameliorate the efficiency and scalability of system modifications with respect to classic methodologies; (iii) provide an efficient access to attribute values; (iv) be fruitfully exploited in software management systems; (v) guarantee theoretical properties of a grammar, like its termination. This is an extended abstract for the Models 2015 Conference of the journal paper of the same name [1]. I. MOTIVATION Dynamic software architectures enable adaptation in evolving distributed systems. A crucial undesirable implication of such adaptations is a potential loss of correctness, the system withdrawing from its scope of consistency. Besides correctness, the system has evolving non-functional requirements, which are tightly linked to its appropriateness or efficiency. The satisfaction of these objectives depends on the properties of the system, its components, and their relations. On one hand, graph-based models are appropriate for the design of adaptation rules that necessarily preserve the system's consistency. On the other, currently available graph based methods exhibit limitations with regard to the description of system properties, in particular regarding their evolution and inter-dependencies

Graph-based formalism for Machine-to-Machine self-managed communications

International audienceMachine-to-Machine communications comprise a large number of intelligent devices sharing information and making cooperative decisions without any human intervention. To support M2M requirements and applications which are in perpetual evolution, many standards are designed, updated and rendered obsolete. Among these, arise from The European Telecommunications Standards Institute (ETSI) a promising standard for M2M communications. The ETSI M2M provides in particular a standardized framework for interoperable M2M Services. As most of its peer, this standard does not, however, address the issue of dynamic reconfiguration or provide a suitable model for the reasoning required to build self-managed M2M architectures. In our paper, we propose a graph-based approach built on top of the ETSI standard, including rules for reconfiguration management, to enforce self-management properties of M2M communications

Generic approach for graph-based description of dynamically reconfigurable architectures

Architectural adaptation is studied for handling adaptation in autonomic distributed systems. It is achieved by implementing a model-based approach for managing reconfiguration of dynamic architectures. Describing such architectures includes defining rules for describing both architectural styles and theirs reconfiguration mechanisms. Within this research context, the work presented in this paper is conducted using formal specification based on graphs and graph rewriting appropriately for tackling architectural adaptation problems. A graph-based general approach for describing architectures and handling their dynamic reconfiguration is introduced. Our approach is illustrated in the context of a distributed hierarchical application. The formal models that allow the generation of a graph grammar for dynamic architecture description and the automatic definition of transformation rules for achieving intern self-protecting during the adaptation are elaborated