A Few Results on Non-Preemptive Real Time Scheduling

In this paper, we investigate the non-preemptive scheduling problem as it arises in single processor systems. We focus on non-idling scheduling, the idling scheduling is briefly introduced in the last section. We extend some previous published results concerning preemptive and non-preemptive scheduling over a single processor. The main issue that we study in this article is the applicability and/or adaptation of results obtained in preemptive scheduling. In a first part we embark on revisiting aperiodic non idling non preemptive scheduling. We review complexity results and investigate conditions under which Earliest Deadline First is optimal in non preemptive scheduling. In a second part, we scrutinize periodic non idling non preemptive scheduling and we show that for non preemptive scheduling feasibility must be checked on a time interval of duration r+2P (r denotes the maximum of the release times and P the smallest common multiple of the task periods). We also show that a well established result concerning feasibility of task sets under non preemptive scheduling (no overload on any given time intervals) has no equivalence in non preemptive scheduling even if one takes into account the blocking factor. The third part is a very quick introduction to scheduling problems in an idling and non preemptive context

Real-time communications over broadcast networks : the CSMA-DCR and the DOD-CSMA-CD protocols

Projet REFLECSRésumé disponible dans le fichier PD

A Few Results on Non-Preemptive Real Time Scheduling

In this paper, we investigate the non-preemptive scheduling problem as it arises in single processor systems. We focus on non-idling scheduling, the idling scheduling is briefly introduced in the last section. We extend some previous published results concerning preemptive and non-preemptive scheduling over a single processor. The main issue that we study in this article is the applicability and/or adaptation of results obtained in preemptive scheduling. In a first part we embark on revisiting aperiodic non idling non preemptive scheduling. We review complexity results and investigate conditions under which Earliest Deadline First is optimal in non preemptive scheduling. In a second part, we scrutinize periodic non idling non preemptive scheduling and we show that for non preemptive scheduling feasibility must be checked on a time interval of duration r+2P (r denotes the maximum of the release times and P the smallest common multiple of the task periods). We also show that a well established result concerning feasibility of task sets under non preemptive scheduling (no overload on any given time intervals) has no equivalence in non preemptive scheduling even if one takes into account the blocking factor. The third part is a very quick introduction to scheduling problems in an idling and non preemptive context

Preemptive and Non-Preemptive Real-Time UniProcessor Scheduling

Projet REFLECSScheduling theory, as it applies to hard-real-time environment, has been widely studied in the last twenty years and it might be unclear to make it out within the plethora of results available. Our goal is first to collect in a single paper the results known for uniproces sor, non-idling, preemptive/non-preemptive, fixed/dynamic priority driven contexts, consid ering general task sets as a central figure for the description of possible processor loads. Second to establish new results when needed. In particular, optimality, feasibility conditions and worst-case response times are examined largely by utilizing the concepts of workload, processor demand and busy period. Some classic extensions such as jitter, resource sharing are also considered. Although this work is not oriented toward a formal comparison of these results, it appears that preemptive and non-preemptive scheduling are closely related and that the analysis of fixed versus dynamic scheduling might be unified according to the concept of higher priority busy period. In particular, we introduce the notion of deadline-d busy period for EDF sched ules, that we conjecture to be an interesting parallel of the level-i busy period, a concept already used in the analysis of fixed priority driven scheduling

Optimality and non-preemptive real-time scheduling revisited

Projet REFLECSIn this paper, we investigate the non-preemptive scheduling problem as it arises with single processor systems. We extend some previously published results concerning preemptive and non-preemptive scheduling over a single processor. We examine non-idling and idling scheduling issues. The latter are of particular relevance in the case of non-preemption. We first embark on analyzing non-idling scheduling. The optimality of the non-idling non-preemptive Earliest Deadline First scheduling policy is revisited. Then, we provide feasibility conditions in the presence of aperiodic or periodic traffic. Second, we examine the concept of idling scheduling, whereby a processor can remain idle in the presence of pending tasks. The non-idling non-preemptiv- e Earliest Deadline First scheduling policy is not optimal since it is possible to find feasible task sets for which this policy fails to produce a valid schedule. An optimal algorithm to find a valid schedule (if any) is presented and its complexity analyzed. This paper shows that preemptive and non-preemptive scheduling are closely related. However, non-preemptive scheduling leads to more complex problems when combined with idling scheduling

Real-Time Fixed and Dynamic Priority Driven Scheduling Algorithms: Theory and Experience

Projet REFLECSThere are two main positions regarding real-time scheduling algorithms. The first is based on fixed priorities and the second makes use of dynamic priorities such as deadlines. These two approaches have never really been compared because the emphasis has always been on the ease of implementation rather than the efficiency of the algorithms and the complexity of the associated feasibility conditions. In addition to traditional real-time applications, we believe that starting to look at these two criteria will be very important in the perspective of providing admission control mechanisms and real-time guarantees on large distributed systems like the Internet network. To that end, our purpose is first to provide a general framework based, on the one hand, a representation of preemptive, real-time scheduling in an algebraic structure that enables us to evaluate the distance of the optimality of any scheduling algorithm ; and on the other hand, a consistent representation of the associated feasibility conditions that enables us to evaluate the number of basic operations. As a second step, considering several kinds of traffics, we initiate the comparison by a straight, but limited, application of our general framework. Our preliminary results will notably highlight, in the cases where deadlines are all greater than periods, that fixed priority schedulers (like deadline monotonic) behave as well as EDF while the worst-case response time analysis is less complex. The same remark is valid when the task sets are almost homogeneous but is in favor of EDF in the general case or when a simple feasibility analysis is needed. Therefore, it might be of interest, given a real-time scheduling context (spanning from small embedded system to large distributed system), to take into account these two extra criteria in order to find a right trade-off among several possible solutions

Non-functional Data Collection for Adaptive Business Processes and Decision Making

International audienceMonitoring application services becomes more and more a transverse key activity in SOA. Beyond traditional human system administration and load control, new activities such as autonomic management as well as SLA enforcement raise the stakes over monitoring requirements. In this paper, we address a new monitoring-based activity which is selecting among competitive service offers based on their currently measured QoS. Starting from this use case, the late binding of service calls in SOA given the current QoS of a set of candidate services, we first elicit the requirements and then describe M4ABP (Monitoring for Adaptive Business Process), a middleware component for monitoring services and delivering monitoring data to business processes wishing to call them. M4ABP provides solutions for general requirements: flexibility as well as performance in data access for clients, coherency of data sets and network usage optimization. Lessons learned from this first use case can be applied to similar monitoring scenario, as well as to the larger field of context-aware computing

Les médicaments génériques en France : état des lieux en 2017 et illustrations au travers d’analyses comparatives au sein de quelques groupes génériques du répertoire national

De nos jours, la substitution par les médicaments génériques en France rencontre toujours une certaine méfiance, tant de la part des patients, que de certains professionnels de santé. Partant de ce constat, ce travail a pour but de lever certaines inquiétudes concernant les médicaments génériques. Pour cela, un état des lieux le plus actualisé et complet possible est effectué. Les différentes définitions, aspects réglementaires et obligations concernant les médicaments génériques en France, ainsi que dans plusieurs pays occidentaux sont abordées. La notion de bioéquivalence est également détaillée, ainsi que l’origine de fabrication des médicaments génériques, très majoritairement européenne. Le marché du médicament générique Français est ensuite évoqué d’un point de vue économique. Il est comparé à celui de nos voisins Anglais et Allemands et des Etats-Unis, qui sont des marchés plus développés. Par la suite, les causes de méfiance concernant les médicaments génériques chez les patients, pharmaciens et médecins sont déterminées, au travers de la lecture d’une méta-analyse parue en 2015 qui illustre en partie les freins au développement du générique en France. Finalement, une comparaison qualitative des différentes formulations excipiendaires employées au sein de plusieurs groupes génériques de la classe des antidépresseurs de forme orale solide est effectuée. Il ressort de ces analyses que lorsqu’il y a modification de la nature d’un ou de plusieurs excipients, celle-ci n’entraîne aucune variation significative de la biodisponibilité du médicament générique versus le médicament de référence, ceci permettant de rassurer quant à leur emploi

QoS Policies for Business Processes in Service Oriented Architectures

International audienceThe advent of Service Oriented Architectures tends to promote a new kind of software architecture where services, exposing features accessible through highly standardized protocols, are composed in a loose coupling way. In such a context, where services are likely to be replaced or used by a large number of clients, the notion of Quality of Service (QoS), which focuses on the quality of the relationship between a service and its customers, becomes a key challenge. This paper aims to ease QoS management in service compositions through a better separation of concerns. For this purpose, we designed QoSL4BP, a domain-specific language which allows QoS policies specification for business processes. More specifically, the QoSL4BP language is designed to allow an architect to specify QoS constraints and mechanisms over parts of BPEL compositions. This language is executed by our ORQOS platform which cooperates in a non-intrusive way with orchestration engines. At pre-deployment time, ORQOS platform performs service planning depending on services QoS offers and on the QoS requirements in QoSL4BP policies. At runtime, QoSL4BP policies allow to react to QoS variations and to enact QoS management related mechanisms

A Declarative Approach for QoS-Aware Web Service Compositions

International audienceWhile BPEL language has emerged to allow the specification of Web Service compositions from a functional point of view, it is still left to the architects to find proper means to handle the Quality of Service (QoS) concerns of their compositions. Typically, they use ad-hoc technical solutions, at the message level, that significantly reduce flexibility and require costly developments. In this paper, we propose a policy-based language aiming to provide expressivity for QoS behavioural logic specification in Web Service orchestrations, as well as a non-intrusive platform in charge of its execution both at pre-deployment time and at runtime