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Multiprocessor Scheduling In this chapter, we limit the study to multiprocessor systems with centralized control that are called ‘strongly coupled systems’. The main characteristics of such systems are the existence of a common base of time (for global scheduling of events and tasks) and a common memory (for implementing the vector of communication between tasks). Consequently, one has a global view of the state of the system accessible at every moment. | Scheduling in Real-Time Systems. Francis Cottet Joëlle Delacroix Claude Kaiser and Zoubir Mammeri Copyright 2002 John Wiley Sons Ltd. ISBN 0-470-84766-2 5 Multiprocessor Scheduling Introduction In this chapter we limit the study to multiprocessor systems with centralized control that are called strongly coupled systems . The main characteristics of such systems are the existence of a common base of time for global scheduling of events and tasks and a common memory for implementing the vector of communication between tasks . Consequently one has a global view of the state of the system accessible at every moment. In addition to the common memory which contains the whole of the code and the data shared by the different tasks the processors can have local memory stack cache memory and so on . These systems present strong analogies with the centralized systems uniprocessor while primarily being different by their capacity to implement parallel execution of tasks. In a multiprocessor environment a scheduling algorithm is valid if all task deadlines are met. This definition identical to the one used in the uniprocessor context is extended with the two following conditions a processor can execute only one task at any time a task is treated only by one processor at any time. The framework of the study presented here is limited to the most common architecture which is made up of identical processors identical speed of processing with an on-line preemptive scheduling. In this book we do not treat off-line scheduling algorithms which are often very complex and not suitable for real-time systems. It is however important to note that off-line algorithms are the only algorithms which make it possible to obtain an optimal schedule by the resolution of optimization problems of linear systems and to handle some configurations unsolved by an on-line scheduling algorithm. First Results and Comparison with Uniprocessor Scheduling The first significant result is a theorem .