EDA222/DIT160 – Real-Time Systems, Chalmers/GU, 2008/2009 Lecture #1 Updated 2009-01-18 Administrative issues Administrative issues Real Real- -Time Systems Time Systems Lectures: (Jan Jonsson) Lectures – Fundamental methods and theory • Real-time programming, run-time systems och scheduling – 15 classroom lectures • Tuesday at 10:00 – 11:45 in lecture room HC2 HC2 7.5 credit points 7.5 credit points • Wednesday at 08:00 – 09:45 in lecture room HC2 HC2 (week 1 only) • Thursday at 13:15 – 15:00 in lecture room HC2 HC2 Docent Jan Jonsson Jan Jonsson Exercise sessions: (Risat Pathan) Exercise sessions – Complementary lectures in programming and theory Department of Computer Science and Engineering • Programming language Ada 95 and laboratory assignment Department of Computer Science and Engineering • Programming in Ada 95 and scheduling theory Chalmers University of Technology Chalmers University of Technology – Seven exercise sessions • Thursday at 15:15 – 17:00 in lecture room HC2 HC2 Administrative issues Course literature Administrative issues Course literature Laboratory assignment: (compulsory) Laboratory assignment Course book: Course book – Concurrent programming in Ada 95 – A. Burns and A. Wellings: • Control system for simulated train system “Real Real- -Time Systems and Programming Languages Time Systems and Programming Languages”, – Criteria for passing Addison-Wesley, 3:rd edition, 2001 • Demonstration of functioning program Complementary reading: Complementary reading • Written report describing solution – K. Tindell, ”Real Real- -Time Systems and Fixed Priority Scheduling Time Systems and Fixed Priority Scheduling” Examination: Examination – Passed laboratory assignment (demonstration + report) Lecture notes: Lecture notes – Passed final written exam (March 10 at 14:00, in the V building) – Copies of PowerPoint presentations – Grades: Failed, 3, 4, 5 – Blackboard scribble – Successful examination ⇒ 7.5 credit points 1
EDA222/DIT160 – Real-Time Systems, Chalmers/GU, 2008/2009 Lecture #1 Updated 2009-01-18 Information Information Course aim Course aim Student reception: Student reception After the course After the course, the student , the student should should be be able able to: to: • Construct concurrently executing software for real-time – Wednesdays at 13:15 – 13:45 applications that interface to input/output units such as – Room 4479 (floor 4), EDIT building, Rännvägen 6 B sensors and actuators. Student portal: Student portal • Describe the principles and mechanisms used for designing – Administration of laboratory assignment (form groups, booking) real-time kernels and run-time systems. – Results from the grading of written exam and lab report • Describe the mechanisms used for time-critical scheduling Information board: of tasks. Information board • Apply the basic analysis methods used for verifying the URL: http://www.cse.chalmers.se/edu/course/EDA222/ temporal correctness of a set of executing tasks. Lecture notes will be available on the information board no later than 48 hours before the corresponding lecture. Course contents Course contents Course contents Course contents What this course is all about: What this course is not not about: about: What this course is all about: What this course is 1. Construction methods for real-time systems – Design of high-performance computer systems – Design of logically correct programs Specification, implementation, verification – – Distributed computations in multiprocessor systems Application constraints: origin and implications – – Complexity theory for scheduling algorithms 2. Programming of concurrent real-time programs – Scheduling in overloaded systems Task and communication models (Ada95) – – ... Low-level (I/O and interrupt) programming (Ada95) – 3. Verification of system’s temporal correctness Presented in advanced course EDA421 Fundamental scheduling theory – Derivation of worst-case task execution times – 2
EDA222/DIT160 – Real-Time Systems, Chalmers/GU, 2008/2009 Lecture #1 Updated 2009-01-18 What is a real What is a real- -time system? time system? What is a real What is a real- -time system? time system? It is not only It is not only about high about high- -performance computing! performance computing! “A real-time system is one in which the Real Real- -time systems time systems must meet must meet timing constraints timing constraints correctness of the system depends not only on the High High- -performance computing performance computing maximizes average maximizes average throughput throughput logical result of computation, but also on the time at which the results are generated” Average performance says nothing about correctness! Average performance says nothing about correctness! “A statistician drowned while crossing a stream A statistician drowned while crossing a stream “ J. Stankovic, “Misconceptions of Real-Time Computing”, 1988 that was, on average, 6 inches deep” that was, on average, 6 inches deep ” Real- Real -time system are instead usually optimized with respect to time system are instead usually optimized with respect to perceived perceived ” ”robustness robustness” ” (control systems) or (control systems) or ”comfort ” comfort” ” (multimedia) (multimedia) What is a real- -time system? time system? What is a real- -time system? time system? What is a real What is a real Properties of a real- Properties of a real -time system: time system: Examples of real- -time systems: time systems: Examples of real • Strict timing constraints • Control systems – Responsiveness (deadlines), periodicity (sampling rate) – Manufacturing systems; process industry – Constraints can (ought to) be verified – Cars, aero planes, submarines, space shuttles • Application-specific design • Transaction systems – Embedded systems – E-commerce; ticket booking; teller machines; stock exchange – Carefully specified system properties – Wireless phones; telephone switches – Well-known operating environment • Multimedia • High reliability – Computer games; video-on-demand – Thoroughly-tested components – Virtual reality – Works even in presence of component faults (fault tolerance) 3
EDA222/DIT160 – Real-Time Systems, Chalmers/GU, 2008/2009 Lecture #1 Updated 2009-01-18 Real- Real -time system components time system components Designing a real Designing a real- -time system time system Application software What should be done & Application is organized as New design! When should it be done? concurrent tasks tasks Administrates scheduling P 2 P 4 and communication between P 3 P 1 executing tasks Specification How should it be done? Run-time system Implementation S Operator S panel Can it be done with the Target given implementation? N 1 S environment Operator Verification A N 2 N 3 display A Processor architecture Specification Specification Specification Specification Examples of application constraints: Examples of application constraints: Specification Specification Implementation Implementation • Timing constraints – A task must complete its execution within given time frames (example: task periodicity or deadline) Requirements Requirements: Constraints Constraints: • Exclusion constraints – A task must execute a code region without being interrupted Reliability Replication (example: a task needs exclusive access to a shared resource) Sampling rate Periodicity • Precedence constraints Response time Deadline – A task must complete its execution before another task can start (example: a data exchange must take place between the tasks) Resources Locality 4
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