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Introduction of EOSEmbedded Real-Time Operating Systems

Introduction Real-Time Scheduling

VxWorksuCLinux Real-Time LinuxuC/OS-II

資工系網媒所 NEWS實驗室/802

Embedded OS trends 2001-2002, sorted by 2001 usage

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bedded Linux

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Embedded OS trends 2001-2002, sorted by 2002 expectation

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orks

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Real-Time Systems vs. Embedded Systems

RTS ESRTES

.Radar .Calculator.ABS


Real-Time Systems

Time

Value

Hard RTS

Soft RTS

FirmRTS

Deadline

-Value


RTOS at a Glance- http://www.onesmartclick.com/rtos/rtos.html

AMX, KwikNet, KwikPeg (from KADAK Products Ltd.) C EXECUTIVE (from JMI Software Systems, Inc.) CMX-RTX (from CMX Systems, Inc.)

DeltaOS (from CoreTek Systems, Inc.)

eCos (from Red Hat, Inc.)

embOS (from SEGGER Microcontroller Systeme GmbH) eRTOS (from JK microsystems, Inc.)

ETS (from VenturCom)

EYRX (from Eyring Corporation)

INTEGRITY (from Green Hills Software, Inc.)

INtime® real time extension to Windows® (from TenAsys Corporation)

IRIX (from SGI)

iRMX (from TenAsys Corporation)

Jbed (from esmertec, inc.)

LynxOS (from LynuxWorks)

MQX (from Precise Software Technologies Inc) Nucleus PLUS (AcceleratedTechnology, ESD Mentor Graphics)

On Time RTOS-32 (from On Time Informatik GmbH)

OS-9 (from Microware Systems Corporation)

OSE (from OSE Systems )

PDOS (from Eyring Corporation)

PSX (from JMI Software Systems, Inc.)

QNX Neutrino (from QNX Software Systems Ltd.)

QNX4 (from QNX Software Systems Ltd.)

REDICE-Linux (from REDSonic, Inc.)

RTLinux (from Finite State Machine Labs, Inc.)

RTX 5.0 (from VenturCom)

Portos (from Rabih Chrabieh)

smx (Micro Digital, Inc.)

SuperTask! (from US Software)

ThreadX (from Express Logic, Inc.)

Treck MicroC/OS-II (from Elmic Systems USA, Inc.)

TronTask! (from US Software)

TTPos: (from TTTech Computertechnik AG)

VxWorks 5.4 (from Wind River)

SCORE, DACS and TADS (from DDC-I)

Nimble - the SoC RTOS (from Eddy Solutions)

Nucleus (from Accelerated Technology)

Fusion RTOS (from DSP OS, Inc.)

FreeRTOS (from Richard Barry)


What is a Real-Time System?

A system enforcing timing constraints, e.g. Avionics, Missile Control, …

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

Real-Time vs. High Performance

What is a timing constraint?A constraint of timing requirements, e.g. period, distance, deadline, ready time, …

Functional and temporal correct.


Real-Time Task Model

Periodic Task Model

parameters are known a priori

worst-case execution time

period

request time ready time deadline start finish preempt resume

Predictability vs. Schedulability

high predictability and schedulability

easy-to-check schedulability condition


Real-Time System ExamplesIndustrial and automation systemComputer networking systemGaming and multimediaMedical instrument and devicesFinancial transaction applicationsMilitary defense systemSecurity monitoring and response systemData acquisition systemMachine vision/translation system…


Time-Driven Scheduling Approachwidely used

inflexible, efficient

large space needede.g. cyclic executive

Priority-Driven Scheduling Approachdynamic-priority

e.g. earliest deadline first

fixed-priority e.g. rate monotonic

0 3 6

0 3 6

Scheduling Approaches


Rate Monotonic

Job with smaller period gets higher priority.

Priority assignment is fixed (static).

0 3 61 2 4 5

1/2

1/3

1/6


Earliest Deadline First

Job with earlier deadline gets higher priority.

Priority is changing dynamically.

0 3 61 2 4 5

1/2

2/6


Earliest Deadline First : optimal dynamic-priority scheduler

job with earlier deadline gets higher priority

schedulability condition1

Rate Monotonic : optimal fixed-priority scheduler

job with smaller period gets higher priority

schedulability condition n (2

1/n- 1)

i

i

i

pe

Periodic Real-Time Schedulers


video serverinter-frame distance must be less than 33ms

robot arm movementneeds steady and smooth operations

satellite/cellular phone trackingservice in constant time interval

more predictable inter-execution time than the periodic task(PT) model

worst inter-execution time for PT is 2xperiod-ei

Distance-Constrained Task Model


Study of Pinwheel Scheduling

n tasks are schedulable on a node (using Sr) if the total utilization is less than or equal to n(2

1/n - 1).

n tasks are schedulable on all nodes (using DSr) if the utilization on any node is ≦2

1/n-1.

Algorithm of O(n) to minimize the total task delays between two nodes.

Algorithm of O(mn) to minimize the total end-to-end delays on m nodes.


Time-driven Scheduling Approach

on-line approachexecute tasks according to off-line generated schedule or parameters

more flexible

off-line approachconstruct complete schedule

exponential time and space

generate effective time parametersstart time, resume time, finish time

optimization

0 3 6


SSr: Pinwheel Schedule Constructor

Generate start times and finish times in O(n2)

task5

5.30 10.6 15.9

task1

21.2

task2

task3

task4


Pinwheel Transformation

Pinwheel

any numbers multiples

jitterless, predictable

Signalanalog digital

noiseless, ease of control

e.g. CD music

2E.g. A={3,4,6,13} ={3,3,6,12} ={3,3,321, 322}• single-number reduction

30 6 9

A

B

12

(RM)

(PW)


Pinwheel Scheduling Properties

Good jitter control in schedules

Easy-to-check schedulability

Predictable resource accesses

Easy extension for aperiodic tasks

Predictable end-to-end delay

Network scheduling (INFOCOM’95 by Han & Shin)

Flexible time-driven approach


Comparison of Schedulers

Scheduler EDF RM Srb

schedulabilitycondition

1 n (21/n - 1) n (21/n - 1)

jitter high low* none

end-to-end delay long short shortest

resource reservation difficult easy* easy

worst caseblocking time

large large small

systemoverload

unstable stable stable

*for higher priority tasks


RTOS

IntroductionVxWorksuCLinux Real-Time Linux

uC/OS-II

國立台灣大學資訊工程學系

TORNADO II ：VxWorks


TORNADO II ： VxWorks

Embedded Development Tools

VxWorks Real Time Operating System

Wind Microkernel

Snapshoot of Host Development Tools


The Next Generation of Embedded Development Tools


Host Development Tools (I)

WindViewA logic analyzer for real-time software.

Provides information about context switches, events, and instrumented objects.

CrossWindA remote source-level debugger.

It is an extended version of the GDB.

WindSHA host-resident command shell.

Provides interactive access from the host to all run-time facilities.


Host Development Tools (II)

BrowserA system-object viewer, a graphical companion to the Tornado shell.

Provides display facilities to monitor the state of the target system.

CodeTestIt is a visualize tool to design code coverage analysis and tracking dynamic memory allocation.

Provides source code viewer-coverage and memory allocation by function.

Look!For C++ development, look inside source level bugs, to see object relationship, and all messages among objects.


Host Development Tools (III)

WindNavigatorIt performs hierarchical browsing on the application code at working project mode by parsing source tree.

StethoscopeIt is a unique real-time graphic data monitor tool.

Watching any variable, see peak values, and look for otherwise miss.

Project ManagerSimplifies organizing, configuring, and building VxWorks applications.


Host Development Tools (IV)

SimulatorIt is a port of VxWorks to the host system.

Simulates a target operating system.

3rd Party ToolsMore than 300 partners provide solutions.

Custom ToolsAn open extension architecture makes sample to custom tools for using Tornado.

Easy to create custom tool using TCL base tool API.


VxWorks


Wind Microkernel


Embedded Internet


Virtual Memory


Multiprocessing


Graphics


File Systems


Networking


WindView


Stethoscope


RTOS

IntroductionVxWorksuCLinuxReal-Time Linux

uC/OS-II


Introduction to uClinux


uCLinux

What is uClinux

Linux vs. uClinux

Features

Ported microcontrollers and microprocessors

Devices running uClinux

Related web sites


What is uCLinux?

Embedded Linux/Microcontroller Project

Pronounced "you-see-linux"

"Mu" stands for "micro", and the "C" is for "controller "

Derivative of Linux 2.0 kernel

Intended for microcontrollers without Memory Management Units (MMUs)


What is uClinux? (Cont.)

First ported to the Motorola MC68328: DragonBall Integrated Microprocessor.

First target system to successfully boot is the 3Com PalmPilot using a TRG SuperPilot Board.


Linux vs. uClinux

Multitasking can be tricky with Non-MMU microprocessors.

Most user applications that run on top of uClinux, however, will not require multitasking.


Linux vs. uClinux(Cont.)

But uClinux absolutely DOES support multi-tasking.

Although there are a few things that must be keep in mind:

There is no memory protection.

uClinux does not implement fork(); instead it implements vfork().

Stack does not autogrow. There is a compile time option to set the stack size of a program.


Linux vs. uCLinux(Cont.)

Most of the binaries and source code for the kernel have been rewritten to tighten-up and slim-down the code base.

This all means that the uClinux kernel is much, much smaller than the original Linux 2.0 kernel.

Common Linux API

uCkernel < 512 KB

uCkernel + tools < 900 KB


Feature

uClinux retains the main advantages of the Linux operating system.

NetworkFull TCP/IP stack, as well as support for numerous other networking protocols.

File systemsNFS

ext2

MS-DOS

FAT16/32

And more…


Ported Microcontrollers and Microprocessors

uClinux is the leader in portability.Now uClinux is ported to:

Motorola DragonBall, ColdFire, QUICCHitachi H8300ARM7TDMIETRAXIntel i960PRISMAAtari 68kNEC V850E


Devices running uClinux

Aplio’s voice-over-IP telephoneMCU: ARM7TDMI


Devices running uClinux(Cont.)

AXIS 2100 Network CameraMCU: AXIS ETRAX

Place it anywhere - no PC required

High-quality images - up to 10 frames/sec

No extra accessories, software or video cabling needed

Built-in Web server


Related Web Site

Wind River Homehttp://www.windriver.com/

The official site of uClinux:http://www.uclinux.org/


RTOS

IntroductionVxWorksuCLinuxReal-Time LinuxuC/OS-II


Introduction to

Real-Time Linux


Real-Time Linux

UTIME and KURT-Linux

RTLinux

RTAI


UTIMEUTIME and KURT-Linux are developed by the Information and Telecommunication Technology Center (ITTC) at the University of Kansas

UTIME is now a part of the KURT-Linux distribution

http://www.ittc.ku.edu/utime/

Supports Intel 80x86 architecture

In Linux, timing resolution of kernel timer is restricted to 10 ms (80x86 architecture) due to the 100 Hz frequency of timer interrupt

Linux maintains the sense of time at every timer interrupts and handles the kernel timer in the timer interrupt bottom half


Aims of UTIME

Provides microsecond level timing resolution for Linux kernel timer

Reprogram the timer chip of X86 as one-shot or periodic timer at any frequency

Use Time Stamp Counter (TSC register) of Pentium or timer chip itself for non-Pentiums to determine the time in a tick

Fully compatible with Linux kernel APIs and system calls (time(), nanosleep(), gettimeofday())


Implementation of UTIME

Add additional field "usec" to the timer_list structure of Linux which indicates the microsecond within the current "jiffy" that the timer is to timeout

Added a "jiffies_u" variable which tracks the microseconds within a 10ms tick

Call the do_timer() routine (Linux timer interrupt handler) every jiffy by UTIME instead of timer interrupt handler


Using the UTIME

User can take advantage of UTIME byThe nanosleep system call

Interval timers

The select system call

A custom kernel module


UTIME nanosleep example

void nanosleep_test(int delay) {

struct timespec sleepy;

sleepy.tv_sec = 0;

sleepy.tv_nsec = delay * 1000;

nanosleep(&sleepy, 0);

}


UTIME Interval Timer Examplevoid timer_handler(int signal) {

// This is a job of one real-time task}

void setitimer_test(int delay, int interval, int tries) {struct itimerval timer; sigset_t mask; struct sigaction action; int i;

timer.it_interval.tv_sec = 0;timer.it_interval.tv_usec = interval;timer.it_value.tv_sec = 0;timer.it_value.tv_usec = delay;

sigemptyset(&mask); action.sa_handler = timer_handler; action.sa_flags = 0; sigaction(SIGALRM, &action, 0); setitimer(ITIMER_REAL, &timer, 0); for (i = 0 ; i < tries ; i++) { sigsuspend(&mask); } timer.it_interval.tv_sec = 0; timer.it_interval.tv_usec = 0; timer.it_value.tv_sec = 0; timer.it_value.tv_usec = 0; setitimer(ITIMER_REAL, &timer, 0);}


UTIME select and poll Example

void select_test(int delay) {

struct timeval timeout;

timeout.tv_sec = 0;

timeout.tv_usec = delay;

select(0, 0, 0, 0, &timeout);

}

void poll_test(int delay) {

poll(0, 0, delay);

}


UTIME Kernel Module Example1 extern unsigned long volatile jiffies;

2 extern int volatile jiffies_u;

3 void timer_handler(unsigned long data) {

4 struct timeval now;

5 gettimeofday(&now, NULL);

6 }


UTIME Kernel Module Example (cont’d)7 int init_module(void) {8 struct timer_list timer; unsigned long timeout; signed long timeout_u;9 struct timeval now;10 /* Initialize and set the timer to go off in 5ms */11 init_timer(&timer);12 timer.expires = jiffies;13 timer.usec = jiffies_u + 5000;14 if (timer.usec >= USEC_PER_JIFFIES) {15 timer.expires++;16 timer.usec -= USEC_PER_JIFFIES;17 }18 timer.data = 100;19 timer.function = timer_handler;20 timer.flags |= UTIME_OFFSET;21 /* Now add the timer. */22 add_timer(&timer);23 return 0;24 }


Performance of UTIME (Pentium-200)


Performance of UTIME without Pentium (Simulated by Pentium-200)


KURT-Linux

Provide on-demand, microsecond resolution and real-time scheduling capabilities to the standard Linux kernelReal-time process could be kernel function (provide by UTIME) or user-space process using KURT APIhttp://www.ittc.ku.edu/kurt/Event-driven (time-driven) scheduling mechanism that switches tasks in an explicit order

Static real-time schedule – generate an off-line schedule and save it in a file and load this schedule from disk at run-timeDynamic real-time schedule – generate an off-line schedule and submit this schedule at run-time


API of KURT-Linux

KURT Pseudo DeviceOnly three operations, open, close and ioctl

KURT kernel subsystem uses this device to communicate with user space programs

Used by KURT API library

KURT APIDLL which is linked with real-time process

General and Utility operations

Process Initialization, registration, and control

Schedule submission


KURT-Linux Architecture


General and Utility Operationskurt_open() – open an instance of the KURT pseudo device before doing any KUT API callsget_num_rtprocs() – return the number of real-time processes in KURTget_rtstats() – reports a process’s real-time behaviorget_rt_id_from_name() – retrieve a process’s real-time id via name lookupevent_stats() – prints real-time timer statistical informationproc_stats() – prints statistical information for all real-time processesset_scheduling_offset() – set the delay setting of UTIME, default is 20 microsecondsget_scheduling_offset() – get the delay setting of UTIME


Process Initialization, Registration, and Control

rt_suspend() – suspends a real-time process

set_rtparams() – sets, resets, or unsets the real-time parameters for a process

get_rtparams() – retrieves the real-time parameters for a process


Schedule Submission

rt_schedule_events() - submits a binary schedule file of contiguous real-time timers to the kernelset_scheduling_task() / clear_scheduling_task() – registers/unregisters current process as the KURT scheduling task, which is the only one task to assign the schedule to KURT-Linuxswitch_to_rt() – switches the kernel to a specific real-time modeswitch_to_normal() – disables real-time schedulingsubmit_dynamic_schedule() – submits a binary schedule of real-time timers type rt_timer_list into the kerneldisable_dynamic_schedule() – disables the dynamic scheduling facilities


Real-Time Linux


RTLinux

RTAI


RTLinux

Hard real-time operating systemCoexists with Linux or BSD kernelRTLinux itself is non-preempriveRuns Linux as a lowest priority threadWorst case interrupt latency on a x86 is less than 15 microseconds from the moment the hardware interrupt is assertedUses a standard GDB DebuggerRuns on x86, PowerPC, Alpha, and MIPSProvides POSIX threads and signalshttp://fsmlabs.com


Tasks in RTLinux

Real-time tasks in RTLinux are written as special Linux modules

Runs in the kernel space

Privileged

Do not use virtual memory.

RT-FIFOA user space process

Do system calls for RTLinux thread


Detail of the bare Linux kernel

Hardware

UNIX/Linux kernelDevice Drivers

Hardware InterruptsI/O

System Libraries

User Processes


RTLinux Kernel Architecture

Hardware


UNIX/Linux kernelDevice Drivers

System Libraries

User Processes

RTLinux Plugin


Linux is executed in the background

Real-time tasks

RT SchedulerDirectHardware

Access


Data Flow in an RT Application


RTLinux APIs

Basic APICreating RTLinux POSIX threadsTime facilitiesConversion routinesScheduling threads (priority-driven scheduler)

Advanced APIFloating point operations supportRTLinux IPC

Real-time FIFOsShared memoryWaking and suspending RTLinux threadsMutual exclusion

Accessing memoryInterrupts


Real-Time Linux


RTLinux

RTAI


RTAI

Variant of RTLinux

http://www.aero.polimi.it/~rtai/

RTAI supports X86, PowerPC, ARM (StrongARM; ARM7: clps711x-family, Cirrus Logic EP7xxx, CS89712), and MIPS

Using RTHAL to trap LinuxA structure which contains function pointers and variables of Linux

Trap Linux kernel by replacing the function pointers in RTHAL


Architecture of RTAI

資工系網媒所 news 實驗室 18:40 /800 introduction of eos embedded real-time operating...

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