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Real Time Versions ofLinux Operating System

Present by 

Tr n Duy Th nhầ ịQuách Phát Tài

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ContentImplement core real-time Linux

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1. Standard Linux• Memory

Management• Memory

Protection• che!uling an!

Tas" Management• #ar!$are

Inter%aces•

&ile Management•

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2. Real-time Linux kernel

+ Mo!i%ications that ma"e Linux ,eal Time

+ ,eal-Time Patches to the tan!ar! ernel

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2. Real-time Linux kernelMo!i%ications that ma"e Linux ,eal Time

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2.1 Modification that make Linux

Real-time+ Interrupt processing in standard kernel( 2 hal0es

The bottom-hal% tas" is the interrupt han!ler an! rea!s !ata

%rom the physical !e0ice into a memory bu%%er The top-hal% tas" rea!s %rom the memory bu%%er an! passes the

!ata to a "ernel accessible bu%%er

+ In the standard kernel( $ithout preemption) all interruptsare !isable! $hen the bottom-hal% tas" is running

+ 3ll 0ariants o% real-time Linux ha0e intro!uce! mo!i%icationsat the "ernel le0el re!uce both the interrupt latency an! 4itter bet$een perio!ic

interrupts

%aster response to external e0ents an! higher resolution timing

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2.1 Modification that make Linux Real-time

+ tan!ar! "ernelpreemption

+ #igher priority "ernelprocesses can preemptlo$er priority 

+ Linux 0ersion 2/.

+ latency an! 4itter isaroun! 1 millisecon!

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2.2 Real-time Patches to the StandardKernel

a!!ing a secon!) highly e%%icient) "ernel to han!le real-timetas"s

Micro ernel( ,TLinux) ,T3I 7ano ernel

,esource ernel 8xtension

ma"ing changes !irectly to the stan!ar! "ernel

P9I: ,eal-Time 8xtensions( implement the timers) signals)semaphores) process memory loc"ing) share! memory)prioritysche!uling) synchroni;e! an! asynchroni;e! I,T

Timeys Linux

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2.2.1 Micro Kernel•  @ictor Ao!ai"en controls

the execution o% real-time

tas"s• runs the stan!ar! Linux

kernel as abackground task

• RTLinux – New Mexico Tech

• RTAI - Politecnico !i

Milano

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2.2.2 Nano Kernel

+ 3!apti0e Domain8n0ironment %or9perating ystems

C3D89+ similar to the micro"ernel

+ many operating

systems+ can be run in parallel

on top o% the nano-"ernel layer

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2.2.3 Resource Kernel xtension

+ pro0i!es a gate$ay toresources such as %ilesystems) serial an! parallelports) an! net$or"inter%aces %or both the

normal "ernel an! also %oruser processes

+ control the interruptpreemption issues %or the

stan!ar! "ernel+ >ser-space can

communicate !irectly 

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2.2.! P"S#$ Real-time xtensions

Mo!i%y !irectly to the stan!ar! "ernel

Implement the timers) signals) semaphores) process memoryloc"ing) share! memory)priority sche!uling) synchroni;e! an!asynchroni;e! Ini0ersity ,eal-Time Linux C>,T!istribution)

high resolution timers)

real-time sche!uling impro0ements

TimeSys Linux ma"ing the stan!ar! "ernel preemptable

inclu!ing a "ernel sche!uler that pro0i!es sche!uling %or the bottom-hal% "ernel interrupt processing an! %or interrupts themsel0es

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2.3 Performance Com%arison

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Real-time versions of Linux

+ Open-Source Distributions: Pro0i!e the source co!e an! buil! scripts so the

user can un!erstan!) mo!i%y) an! buil! the co!e

Documentation may be sparse an! technicalsupport nonexistent

+Commercial Distributions Ma"e a pro%it to stay in business upport an! !ocumentation

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3. Open-Source Distribution

+ 3D89

+ >,T

+ ,T3I

+ ,TLinux

+ Timeys Linux EPL

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Open-Source: D!OS

+ 3!apti0e Domain 8n0ironment %or 9peratingystems

+ 2==2

+ Is a har!$are abstraction layer

+ 3llo$ a real-time "ernel an! a general purpose

"ernel to co-exist+ ,eal-Time Mechanism nano-"ernel

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Open-Source: "#RT

+ ansas >ni0ersity 

+ 1BB6

+ Implement the P9I: real-time extensions toLinux

+ The patches implement the Fueue! real-time

signals an! the high-resolution timers+ ,eal-Time Mechanism( P9I: timers an!

sche!uling

+ 1=s o% microsecon!s o% latency an! 4itter

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Open-Source: RT$ %Linux-RT&

+ Politecnico !i Milano) Italy

+ 2===

+ 9riginally base! on ,TLinux

+ 80ol0e! as a uniFue %a0or o% real-time Linux

+ ,eal-Time Mechanism( micro "ernel

+ G 1= microsecon!s latency an! 4itter

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Open-Source: RTLinux+ @ictor Ao!ai"en) 7e$ Mexico Institute o%

Technology 

+ 1BB5

+ 'o0ers the logic o% running stan!ar! Linux as a bac"groun! threa! to the real-time tas"s

+ ,eal-Time Mechanism( micro "ernel+ G 1= microsecon!s latency an! 4itter

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Open-Source: TimeSys Linux '(L+ Timeys

+ 1BB?

+ Pro0i!es a preemptable "ernel an! an impro0e!tas" sche!uler

+ ,eal-Time Mechanism( Preemptable ernel

+ G 1== microsecon!s o% latency an! 4itter

2=

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). *ommercial Distribution+ ,e!#a$" Linux

+ &MLabs ,TLinux

+ Monta@ista Linux

+ Q,T

+ ,8DI'8-Linux

+ Linux MP+ Timeys

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*ommercial: Re+,a Linux

+ 'oncurrent 'omputer 'orporation

+ Pac"age! har!$are

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*ommercial: 0ontaVista Linux

+ Monta@ista o%t$are Inc

+ Tailor to the nee!s o% embe!!e! so%t$are!e0elopers

+ ,eal-Time Mechanism( ernel pre-emptionenhancements

2.

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*ommercial: 1RTS

+ Quality ,eal Time ystems

+ De0elops applications %or real-time control an!simulation

+ ,eal-Time Mechanism( ,TLinux micro "ernel

2/

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*ommercial: R!D$*!-Linux

+ ,8Donic Inc

+ Integrates the !ual "ernel approach an! thepreemptable "ernel to pro0i!e a hybri! solution

+ ,eal-Time Mechanism( Micro "ernel an! ernelPreemption

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*ommercial: Linux S0(

+ ynergy Microsystems Inc

+ upport ,TLinux as the operating system ontheir Po$erP' single-boar! computers

+ ,eal-Time Mechanism( ,TLinux micro "ernel

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*ommercial: TimeSys Linux2RealTimeTimeSys Linux24et TimeSys Linux2*(#

+ Timeys 'orporation

+ 3!!s three proprietary components into anopen-source preemptable "ernel #igh-resolution timers an! priority inheritance

Euarantee! access to 'P> resources)

Euarantee! access to net$or" resources+ ,eal-Time Mechanism( Preemptable ernel

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&hank 'ou(

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