A reservation scheduler for real time operating systems
This presentation is the property of its rightful owner.
Sponsored Links
1 / 18

A Reservation Scheduler for Real-Time Operating Systems PowerPoint PPT Presentation


  • 40 Views
  • Uploaded on
  • Presentation posted in: General

A Reservation Scheduler for Real-Time Operating Systems. David Matschulat, César Marcon, Fabiano Hessel PUCRS - Brazil. Introduction – Quality of Service. Increase demand for embedded multimedia platforms (health devices, cellphones,…) End-to-end QoS has become harder

Download Presentation

A Reservation Scheduler for Real-Time Operating Systems

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


A reservation scheduler for real time operating systems

A Reservation Scheduler for Real-Time Operating Systems

David Matschulat, César Marcon, Fabiano Hessel

PUCRS - Brazil


Introduction quality of service

Introduction – Quality of Service

  • Increase demand for embedded multimedia platforms (health devices, cellphones,…)

  • End-to-end QoS has become harder

    • new requirements imposed by multimedia systems and new codification techniques have emerged

  • QoS requirements has become essential

  • Quality of Service (QoS)

    • Offer Guarantees

      • Bandwidth

      • Delay

      • Jitter

      • Deadline miss rate


Introduction qos for operating systems

Introduction – QoS for Operating Systems

  • Mapping

    • What?

  • Admission Test

    • When?

  • Resource Reservation Protocol

    • How?

  • In a end-to-end manner.

    • Some applications demand end-to-end predictability.

    • Each part of a Operating System can (or should) take part in the end-to-end quality provision.


Motivation

Motivation

  • Flexibility and predictability are desirable for applications and can be accomplished through end-to-end QoS provision.

  • The Process Scheduler of an OS is a key player for QoS provision.

  • Current solutions do not offer hard real-time coexistence support with other task classes.


Job and task models

Job and Task Models

  • Task is a set of Jobs

  • Each Job has a Release time, Execution time, Relative deadline and Absolute deadline


R edf reservation based edf

R-EDF – Reservation Based EDF

  • β = Best-effort Reservation

  • Θ(J) = Job Utilization

  • Θ(T) = Task Utilization: the mean utilization of all jobs.

  • Ψ(T) = Peak Utilization: the utilization of its largest job.

  • PCRT = Peak Capacity: sum of the peaks (Ψ) of all jobs of a task.

  • The system is overloaded when PCRT > 1 – β.


R edf reservation based edf1

R-EDF – Reservation Based EDF

  • A task reserves Θ(T), its mean utilization.

  • The overrun state protects the system.

  • A job enters the overrun state when its reservation is reached.

  • Admission control is limited by ΣΘ(T) <= 1.


R edf reservation based edf2

R-EDF – Reservation Based EDF

CPU Reservation: R-EDF has room for improvement:

  • Better performance for soft real-time tasks.

  • Support for hard real-time tasks.


Er edf enhanced r edf

ER-EDF – Enhanced R-EDF

  • Based on R-EDF

  • Includes:

    • Hard real-time support

    • Improved performance for soft real-time tasks

  • Components:

    • Admission Control Algorithm

    • Scheduling Algorithm


Er edf admission control

ER-EDF – Admission Control

  • β= 0.1

  • TA: θ=0.5 (1/2), Ψ=0.66 (2/3)

  • TB: θ=0.33 (1/3), Ψ=0.66 (2/3)


Er edf scheduling

ER-EDF – Scheduling


System architecture soc

Internal

Memory

System Architecture - SoC

  • SoC

    • Xilinx Spartan-3 FPGA

    • MIPS processor + EPOS

    • Serial

    • Display

    • SRAM (1 MB)

    • Internal Memory (8 KB)


Experiment first

Experiment - First


Experiment first1

Experiment - First


Experiment second

Experiment - Second


Experiment second1

Experiment - Second


Conclusions

Conclusions

  • Scheduling plays a important role in QoS provision.

  • A new scheduler, ER-EDF was introduced.

    • Support for hard real-time tasks.

    • Better performance for soft real-time tasks when compared to its predecessor.

    • Fallback to classic EDF when the system is underloaded.

  • The algorithm allows the developer to parameterize the OS to fulfill applications requirements, allowing flexibility and predictability.


Thank you questions

Thank YouQuestions?


  • Login