1 / 15

Real-time Linux Evaluation

Real-time Linux Evaluation. Kalynnda Berens, GRC Kalynnda.Berens@grc.nasa.gov. Definitions.

suzanne
Download Presentation

Real-time Linux Evaluation

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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Real-time Linux Evaluation Kalynnda Berens, GRC Kalynnda.Berens@grc.nasa.gov

  2. Definitions • Embedded System - A combination of hardware and software which together form a component of a larger machine. An embedded system is designed to run on its own without human intervention, and may be required to respond to events in real time. • Real-time OS - an operating system that provides a required level of service in a bounded response time • Hard real-time – absolute deadlines that must be met • Soft real-time – time tolerance within which an event can occur

  3. What is Linux? • Unix “clone”, first created in 1992 by Linus Torvalds • Open source operating system • Commonly used in server environment, now used in desktops and embedded systems • Not useful for real-time systems because: • Fairness scheduling, with limited priority scheduling • Unpredictable, sometimes high latency • Non-deterministic behavior • Coarse timing resolution

  4. Real-Time Linux • Modifications or extensions to standard Linux to allow soft or hard real-time applications to meet timing constraints. • One approach uses a separate real-time “kernel” that runs Linux as the lowest priority task. • Another approach modifies standard Linux for preemptibility, latency, timing, and/or scheduling. • Both open source and commercial versions are available.

  5. Real-time Linux Projects • Flight Linux-a customized copy of a standard Linux distribution, adapted to the unique environment of a spacecraft embedded control computer. • STS-83 experiment used Debian GNU/Linux. • RACSI - the remote Automatic Transfer Vehicle (ATV) control at ISS. • GOAS - Ground Operator Assistant System for the rendezvous operations of ATV. • PLATINO numerical control • iArte - Industrial Automation Real Time Environment • FAA Level C certified flight simulator • Cascade – a RTLinux based GPS receiver

  6. Independent Kernel Variants Linux Process Linux Process User Space Kernel Space Real-Time Task Real-Time Task Standard Linux Kernel Real-Time Micro Kernel Hardware

  7. Kernel Modification Variants Linux Process Linux Process Real-time Process User Space Kernel Space Loadable Module Modified Linux Kernel Preemptible, Micro Timing, and/or Low Latency Loadable Module Hardware

  8. Real-time Linux Variants

  9. Testing Real-Time Linux • Requirements derived from • VxWorks 5.4 Test plan, MSFC • VxWorks AE Test plan, GRC • RTOS properties • Specific test scenarios will be derived from the requirements, plus… • Variant-specific attributes • Known errors, defects, etc. • Results of static analysis (open source)

  10. Test Plan VxWorks 5.4 Linux RTOS Test Plan Specific Linux RTOS Test Plans Variant Specific VxWorks AE Errors RTOS Testing Static Analysis

  11. Tools • Linux Trace Toolkit • Dynamic Probes • kGDB (kernel debugger) • Linux Kernel Crash Dump • Linux Test Project • LMBench • Ballista • strace • System Call Tracker

  12. Scheduling Hardware Interface Communication and Synchronization Memory Management Task Management Timing Configuration External Communications Error Reporting Embedded Features File system Reliability Requirements

  13. Error Catalog

  14. Test Setup Development System (Mandrake 8.1 Linux) Ethernet Connection Embedded PowerPC Embedded Pentium PC/104

  15. Future Work • Static analysis of open source variants • Completion of variant-specific test plans • Test scenario creation • Test procedures for each scenario • Testing on embedded hardware • Test results and report

More Related