real-time scheduling (6)

real-time scheduling (6) - COP 4600: Intro To OS (Real-time...

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Unformatted text preview: COP 4600: Intro To OS (Real-time Scheduling) Page 1 © Dr. Mark Llewellyn COP 4600 – Summer 2011 Introduction To Operating Systems Real-time Processor Scheduling Department of Electrical Engineering and Computer Science Computer Science Division University of Central Florida Instructor : Dr. Mark Llewellyn [email protected] HEC 236, 407-823-2790 http://www.cs.ucf.edu/courses/cop4600/sum2011 COP 4600: Intro To OS (Real-time Scheduling) Page 2 © Dr. Mark Llewellyn Real-Time Systems • Real-time computing is becoming an increasingly important discipline. • The OS, and in particular the scheduler, is perhaps the most important component of a real-time system. • Real-time computing may be defined as that type of computing in which the correctness of the system depends not only on the logical result of the computation but also on the time at which the results are produced. COP 4600: Intro To OS (Real-time Scheduling) Page 3 © Dr. Mark Llewellyn Examples of Real-Time Systems • Control of laboratory experiments • Process control in industrial plants • Robotics • Air traffic control • Telecommunications • Military command and control systems • Medical diagnostic and life-support systems COP 4600: Intro To OS (Real-time Scheduling) Page 4 © Dr. Mark Llewellyn Real-Time Systems • To define a real-time system, we need to define what is meant by a real-time process or task. • In general, in a real-time system, some of the tasks are real-time tasks, and these have a certain degree of urgency associated with them. • Such tasks are attempting to control or react to events that take place in the outside world • Because these events occur in “real time”, a real-time task must be able to keep up with the events with which it is concerned. COP 4600: Intro To OS (Real-time Scheduling) Page 5 © Dr. Mark Llewellyn Real-Time Systems • Usually, a deadline is associated with a particular task. • Deadlines may represent either a start time or a completion time. • Real-time tasks are typically classified as either hard or soft . • A hard real-time task is one that must meet its deadline; otherwise it will cause unacceptable damage or a fatal error to the system. • A soft real-time task has an associated deadline that is desirable but not mandatory; it still makes sense to schedule and complete the task even if its deadline has passed. COP 4600: Intro To OS (Real-time Scheduling) Page 6 © Dr. Mark Llewellyn Real-Time Systems • Another characteristic of real-time tasks is whether they are periodic or aperiodic . • An aperiodic task has a deadline by which it must start or finish, or it may have a constraint on both the start and finish time....
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This note was uploaded on 10/03/2011 for the course COP 4600 taught by Professor Montagne during the Summer '08 term at University of Central Florida.

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real-time scheduling (6) - COP 4600: Intro To OS (Real-time...

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