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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  1. Limited preemption, release jitter and overheads

Impact of Release Jitter

PreviousNon-preemptive schedulingNextAccounting for overheads

Last updated 2 years ago

Impact of the variations on the tasks’ activation instants.

  • Tasks may suffer deviations on the respective activation instants, e.g. when a task is activated by the completion of another one, by an external interrupt or by the reception of a message on a communication port. In such cases the real time lapse between consecutive activations may vary with respect to the predicted values – release jitter.

  • The existence of release jitter must be taken into account in the schedulability analysis, as in such cases the tasks can execute during time instants different from the assumed ones.

Schedulability tests including the impact of Relese Jitter:

  • The presence of release jitter can be modeled by the anticipation of the activation instants of the following task instances.

Computing Rwc i with release jitter (J k ) for preemptive systems with fixed priorities:

Solved iteratively, as usual: