tailieunhanh - Lịch khai giảng trong các hệ thống thời gian thực P6

Joint Scheduling of Tasks and Messages in Distributed Systems This chapter and the next one discuss mechanisms to support real-time communications between remote tasks. This chapter deals with some techniques used in multiple access local area networks and Chapter 7 deals with packet scheduling when the communications are supported by packet-switching networks such as ATM or IPbased networks. | 6 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 Joint Scheduling of Tasks and Messages in Distributed Systems This chapter and the next one discuss mechanisms to support real-time communications between remote tasks. This chapter deals with some techniques used in multiple access local area networks and Chapter 7 deals with packet scheduling when the communications are supported by packet-switching networks such as ATM or IPbased networks. Overview of Distributed Real-Time Systems The complexity of control and supervision of physical processes the high number of data and events dealt with the geographical dispersion of the processes and the need for robustness of systems on one hand and the advent for several years on the market of industrial local area networks on the other have all been factors which resulted in reconsidering real-time applications Stankovic 1992 . Thus an information processing system intended to control or supervise operations for example in a vehicle assembly factory in a rolling mill or in an aircraft is generally composed of several nodes which may be central processing units computers or programmable automata sensors actuators or peripherals of visualization and dialogue with operators. The whole of these nodes is interconnected by a network or by a set of interconnected networks industrial local area networks fieldbuses etc. Pimentel 1990 . These systems are called distributed real-time systems Kopetz 1997 Stankovic 1992 . Several aspects have to be distinguished when we speak about distributed systems. First of all it is necessary to differentiate the physical or hardware allocation from the software allocation. The hardware allocation is obtained by using several central processing units which are interconnected by a communication subsystem. The taxonomy is more complex when it is about the software. Indeed it is necessary to .