М. V. Kavalerov - Ph.D. (Eng.), Department of Automation and Telemechanics, Perm National Research Polytechnic University E-mail: mkavalerov@gmail.com N. N. Matushkin - Dr.Sc. (Eng.), Professor, Department of Automation and Telemechanics, Perm National Research Polytechnic University E-mail: mnn@pstu.ru

Development of information and control systems, as real time systems, involves the use of real-time scheduling techniques, aimed at improving the efficiency in the use of computational resources. For instance, more efficient scheduling of real-time tasks can make more stringent timing constraints to be met on a given hardware of an information and control system. There is a scheduling problem of real-time tasks under fixed-priority scheduling. This problem can be reduced to the problem of task attribute assignment for real-time tasks, namely the assignment of offset, period, and priority for each task. These attributes must guarantee the execution of these tasks such that their timing constraints are met. Many studies have examined the different types of extensions of the standard model of fixed-priority scheduling. Such extensions make it possible to take into account more information about the features of real-time tasks and their constraints. And this serves as a basis for a more effective scheduling of real-time tasks in information and control systems. One of the possible extensions of the standard model of fixed priority scheduling is a transition from the standard constraints expressed with periods and deadlines to the class of linear interval constraints which includes many of timing constraints of control tasks. Such extension has demanded the development of new algorithms of task attribute assignment for tasks with constraints from this class. In previous papers the authors proposed a number of such algorithms that have different values of speed and efficiency. Further increase in efficiency of task scheduling is possible through the extension of the scheduling model by generalizing the release pattern of real-time jobs and removal of the requirement of strict periodicity. Previously, the authors have proposed the concept of R-algorithm for releasing real-time jobs. R-algorithm is a generalization of a periodic release of jobs. Generally, this is an algorithm that determines the release time of each job of a task according to the scheduling information. In this paper, it is shown that in some cases the use of R-algorithm can ensure successful scheduling when a periodic release of jobs cannot cope with this. A simple example is given, which shows a mechanism for increasing the efficiency of scheduling when the proposed approach is used. This increase in efficiency is expressed by a better exploitation of the available computing resources; in particular, it is not required to increase their performance

 

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