Real-Time Systems Fall 2010 Instructor: Mohsen Bashiri Sharif - - PDF document

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ﻢﻴﺣﺮﻟا ﻦﻤﺣﺮﻟا ﷲا ﻢﺴﺑ CE-40453

Real-Time Systems

Fall 2010 Instructor: Mohsen Bashiri Sharif University of Technology Department of Computer Engineering

What is a Real-Time System? A computer system with strict timing constraints. It must provide the right answer g at the right time…

• r suffer

death and destruction! (well, at least serious system malfunction) What is a Real-Time System? (cont’d)

• Formal Definition:

– The correctness of the system depends not only on the logical results of the computation but also on the time at which the results are produced.

• Examples of real-time systems:

– Engine control – Avionic control – Nuclear control – Medical embedded control – Robot control

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Real-Time System Example

Pacemaker

Senses heart rate breathing blood temp Generates electrical pulse(s) User Interface, Communication, Monitor Battery sensor motor Control Law software Plant controlled device

Misconceptions About Real-Time Computing

• Real-time systems = “fast” systems.

– Advances in supercomputer hardware will take care of real-time requirements. – Real-time systems research = performance engineering.

• There is no science in real-time systems design.

– There are universal, widely accepted methodologies for specification and design. – The study of real-time systems = scheduling theory. – Real-time programming is assembly coding, priority interrupt programming, and device driver writing.

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Misconceptions About Real-Time Computing (cont’d)

• Guaranteeing the real-time performance is not

possible because:

– Hardware failure – Software bus

R l i f i i i i

• Real time systems function in a static environment.
• You will never need to build a real-time OS.

Real-Time Challenges!!!

• Specification and verification.
• Scheduling theory.
• Real-time operating systems.
• Real-time programming languages and design

methodology. gy

• Distributed real-time database.
• Artificial intelligence.
• Fault tolerance.

– Performability

• Real-time system architecture.
• Real time communication.

Computer Science: The Art of Compromise (or Abstraction)

Accuracy Space Time From design to implementation, what is more important?

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The Real-Time Blanket “Real-Time” is an added constraint placed on top of every component of a system p p y p y from the hardware to the application.

Overall Class Objective

Good high-level understanding

• f real-time systems.

What are the critical issues during design implementation and testing? design, implementation, and testing?

– Low-level hardware control – Concurrent programming – Real-time scheduling – System modeling – Worst-Case Execution Time analysis (WCET)

What we will see in this course?

– Real-time system characterization, components and modeling – Real-Time Scheduling

• Uni-processor scheduling
• Multiprocessor scheduling
• Schedulability analysis

Pacemaker

Senses heart rate breathing

y y

– Resource management – Measurement of:

• Reliability
• Performance and Performability
• Power consumption

– Real-time communication

g blood temp Generates electrical pulse(s) User Interface, Communication, Monitor Battery

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More specifically ….

General concepts hard or soft real-time, periodic tasks, sporadic tasks, jobs, release times, deadlines, real-time systems components, … Characterization

• f real‐time

systems Scheduling theory, time and timing constraints (system modeling using timed automata), tasks precedence constraints and dependencies, embedded systems, multiprocessor and distributed systems. Scheduling polling, round-robin, preemptive, nonpreemptive, table- d i i it d i R t M t i (RM) D dli driven, priority-driven, Rate-Monotonic (RM), Deadline- Monotonic (DM), Earliest-Deadline First (EDF), … Resource management Motivations, resource access control, resource sharing under EDF, resource management and reclaiming. Timing analysis Schedulability tests, worst-case execution time (WCET), static analysis, dynamic analysis, … System measuring Reliability, performance, performability, and power/energy consumption. Real-time communication Timing constraints in real‐time communication, real‐time communication protocols, x‐by‐wire.

Real-Time Systems

Prerequisites.

– Basic knowledge of operating systems. – Probability and random processes

Textbooks and resources. – J. W. S. Liu, Real‐Time Systems, Prentice Hall, 2000. – Some papers. – Other related text books. Grading policies for CE-40453 Component Per Problem Sets ? Quiz !! ? Project ? ? Midterm 8/16 ? Final Exam ?

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Grading Policies (cont’d)

• Electronic Submission

– Required for any assignment. – Submission to the CW (cw.sharif.edu).

• Late Policy : 3 grace days TOTAL

– LATE means any time after the DEADLINE. – No need to inform anyone.

• The work you turn in must be your own.

– Do not share your problem solution or code with anyone. – DO cite your references. – Do NOT copy text off the web without a citation.

Assignment 0

• What is a task?
• What is a job?
• What is a process?
• Is there any equal word for above words?

y q