Intégration des évènements non périodiques dans les systèmes temps réel : application à la gestion des évènements dans la spécification temps réel pour Java

Abstract : In computer science, real-time systems are composed of tasks. To each task is associated a timing constraint called a deadline. We distinguish two kinds of tasks : the hard ones and the soft ones. Hard tasks have hard deadlines, which must be respected to ensure the correctness of the system. So hard tasks are in essence periodic, or sporadic. Their behavior has been extensively studied. Soft tasks have soft deadlines that the system has to try to respect. When a task arrival model is unknown, i.e. when task is aperiodic, burst arrivals situation can happens, which makes the tasks timing behavior unpredictable. So aperiodic tasks can only have soft deadlines. The studied problem in this thesis is then the joint scheduling of hard periodic tasks with soft aperiodic events, where the response times of soft tasks have to be as low as possible while the guarantee to meet their deadlines has to be given to hard tasks. A lot of solutions have been proposed these past two decades. We distinguish solutions based on resource reservation, like task servers, and solutions which take benefit from system idle times, like the slack stealer techniques. The first version of the Real-Time Specification for Java (RTSJ) was proposed in early 2000. This specification addresses a lot of problems related to the memory management or the scheduling of periodic tasks. But if it proposes a model to write aperiodic events, advanced mechanisms for the integration of such events to handle the above-mentioned problem are not discussed. We propose modifications to the main advanced mixed scheduling mechanisms like the Polling Server (PS), the Deferrable Server (DS) or the Dynamic Approximate Slack Stealer (DASS) in order to make their implementation possible with the RTSJ. Indeed, these algorithms are deeply connected to the system scheduler, and have to be adapted in order to be implemented in a user-land level.We propose extensions to current RTSJ APIs in order to integrate the modified algorithms and to allow the addition of other algorithms in a unified framework. We also propose some modifications to the RTSJ APIs in order to solve some problems we encountered during the integration of modified algorithms, especially in the field of the feasibility analysis algorithms integration in the specification. Finally, we propose the Minimal Approximate Slack Stealer algorithm (MASS), which is independent of the scheduler implementation and has a lower overhead than DASS
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Damien Masson. Intégration des évènements non périodiques dans les systèmes temps réel : application à la gestion des évènements dans la spécification temps réel pour Java. Autre [cs.OH]. Université Paris-Est, 2008. Français. ⟨NNT : 2008PEST0247⟩. ⟨tel-01239912⟩



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