Notes - MIECT
Sistemas Operativos E De Tempo-real
Notes - MIECT
Sistemas Operativos E De Tempo-real
  • Sistemas Operativos e de Tempo-real
  • Basic Concepts About Real-Time Systems
    • Preliminaries
    • Definitions
    • Objective of the Study of RTS
    • Requirements of Real-Time Systems
  • Real Time Model
    • Real Time Model
    • Temporal Control
    • Task states and execution
    • Kernel/RTOS Architecture
      • Time Management Functions
    • Examples of RTOS
  • Practical Class 01
    • Real-Time Services in Linux
    • Using the Linux real-time services
  • Scheduling Basics
    • Basic concepts
    • Scheduling Algorithms
      • Basic algorithms
    • Static Cyclic Scheduling
    • Exercise
  • Fixed Priority Scheduling
    • Online scheduling with fixed priorities
    • Schedulability tests based on utilization
      • Deadline Monotonic Scheduling DM
    • Response-time analysis
  • Practical Class 2
    • Xenomai brief introduction
    • API
    • Developing an application
  • Dynamic Priority Scheduling
    • On-line scheduling with dynamic priorities
    • Analysis: CPU utilization bound
    • Analysis: CPU Load Analysis
    • Other deadline assignment criteria
  • Exclusive Access to Shared Resources
    • The priority inversion problem
    • Techniques for allowing exclusive access
    • Priority Inheritance Protocol
    • Priority Ceiling Protocol
    • Stack Resource Policy
    • Notes
  • Aperiodic Servers
    • Joint scheduling of periodic and aperiodic tasks
    • Aperiodic Servers
    • Fixed Priority Servers
    • Dynamic Priority Servers
  • Limited preemption, release jitter and overheads
    • Non-preemptive scheduling
    • Impact of Release Jitter
    • Accounting for overheads
    • Considerations about the WCET
  • Profiling and Code Optimization
    • Code optimization techniques
      • CPU independent optimization techniques
      • Cache impact
      • Optimization techniques dependent on memory architecture
      • Architecture-dependent optimization techniques
    • Profiling
  • Multiprocessor Scheduling, V1.2
    • Introduction
    • Definitions, Assumptions and Scheduling Model
    • Scheduling for Multicore Platforms
    • Task allocation
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  • Execution time:
  • Response time and regularity
  1. Basic Concepts About Real-Time Systems

Objective of the Study of RTS

PreviousDefinitionsNextRequirements of Real-Time Systems

Last updated 2 years ago

Generally, when a computer system monitors the state of a given physical process and, if necessary, acts on it in time, then it is a real-time system.

All living beings are real-time in relation to their natural habitats, which are its “real-time system”.

On the other hand, when we build (programmable) machines to interact with physical processes, we need to use Operative Systems, Programming Techniques, and Analysis Methods that allow us to have confidence in their ability to carry out correct and timely actions.

The main objective of the study of Real-Time Systems is thus the development of techniques for:

  • Design;

  • Analysis;

  • Verification...

...that allow to assure that a given (computer, in our case) system has an appropriate timing behavior, satisfying the requirements imposed by the dynamics of the system with which it interacts

Regarding the computational activities of RTS, the main aspects to consider are:

  • Execution time;

  • Response time;

  • Regularity of periodic events.

Despite essential, these aspects are far from trivial:

Reasons for this behavior include:

Execution time:

  • Code structure (language, conditional execution, cycles);

  • DMA, cache, pipeline;

  • Operative System or kernel (system calls).

Response time and regularity

  • Interrupts;

  • Multi-tasking;

  • Access to shared resources (buses, communication ports, ...).

Impact of interference on the Worst-case Response Time