real-time scheduling on multi/many-processor: from...

Real-time scheduling on multi/many-processor: from specification to real-time execution

Eric Noulard – [email protected] Centre de Toulouse

DTIM/LAPSE T R 2 0 1 5 , A u g u s t , 2 4 – 2 8 t h 2 0 1 5

ETR2015 – August, 24–28th 2015 – Eric NOULARD – [email protected]

Summary

• Part 1 : The ROSACE Case Studyhttps://svn.onera.fr/schedmcore/branches/ROSACE_CaseStudy/

ROSACE = Research Open-Source Avionics and Control Engineering• Pagetti C, Saussié D, Gratia R, Noulard E, Siron P (2014) The ROSACE

case study: From Simulink specification to multi/many-core execution. In: 20th IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS’14)http://sites.onera.fr/schedmcore/ROSACE

• Part 2 : Tools• SchedMCore toolbox : http://sites.onera.fr/schedmcore/node/1• Prelude : https://forge.onera.fr/projects/prelude • Lustre : https://cavale.enseeiht.fr/redmine/projects/lustrec

mailto:[email protected]

https://svn.onera.fr/schedmcore/branches/ROSACE_CaseStudy/

http://sites.onera.fr/schedmcore/ROSACE

http://sites.onera.fr/schedmcore/node/1

https://forge.onera.fr/projects/prelude

https://cavale.enseeiht.fr/redmine/projects/lustrec

ETR2015 – August, 24–28th 2015 – Eric NOULARD – [email protected]

The ROSACE Case Study

Romain Gratia5, Thomas Loquen1, Eric Noulard1, Claire Pagetti1,4, David Saussie2 and Pierre Siron3

1ONERA - Toulouse, France 2Polytechnique - Montreal, Canada

3ISAE - Toulouse, France4INPT/ENSEEIHT - Toulouse, France5TELECOM ParisTech - Paris, France


4 ETR2015 – August, 24–28th 2015 – Eric NOULARD – [email protected]

ROSACE: outline

● Introduction

● ROSACE (Research Open-Source Avionics and Control Engineering) case study

● Simulink specifications

● Checker

● Examples of implementation

● Perspectives



Trends in avionic domain

Control design level

COTS hardware integration

- Steps: non linear linearization around a flight condition controller synthesis digitalization (sampling periods)

- Tools: Matlab / Simulink

- Coding of elementary blocks: Scade, Lustre, Signal…- Coding of multi-periodic assembly: home made language, manual coding, …

Implementation level

- Automatic code generator- Manual code- Low level services



Avionic use case: Longitudinal Flight Controller 1/2

Longitudinal motion of a medium-range civil aircraft in en-route phase – Cruise: maintains a constant altitude h and a constant airspeed Va– Change of cruise level subphases:

commands a constant vertical speed Vz (rate of climb) • Ex: FL300 → FL320 → FL340 → FL360• FL300 = pressure altitude of 30000 ft



Avionic use case: Longitudinal Flight Controller 2/2

Performance requirements for change of cruise levels- P1 settling time: time required to settle within 5% of the steady-state value- P2 overshoot: maximum value attained minus the steady-state value- P3 rise time: time to rise from 10% to 90% of the steady-state value- P4 steady-state error: difference between the input and the output at t → ∞.



ROSACE Open Source : Why ?

● Offer realistic (evolving) control command avionic case studyOffer research community a way to compare methods and tools in the domain of time-critical avionic application :

● Code analysis● Code generator● Schedulability analysis● Embedded runtime● ...

● Propose reference implementations in various language :● Matlab/Simulink● Prelude manual assembly + C● Generated Prelude + Generated Lustre

● Make every piece of it accessible and modifiable :● https://svn.onera.fr/schedmcore/branches/ROSACE_Case_Study • Prelude compiler : https://forge.onera.fr/projects/prelude • Lustre compiler : https://cavale.enseeiht.fr/redmine/projects/lustrec• SchedMCore toolbox : http://sites.onera.fr/schedmcore


https://svn.onera.fr/schedmcore/branches/ROSACE_Case_Study

https://forge.onera.fr/projects/prelude

https://cavale.enseeiht.fr/redmine/projects/lustrec

http://sites.onera.fr/schedmcore


ROSACE: outline

● Introduction



● Checker


● Perspectives



Longitudinal flight controller architecture

engine

elevator

200 Hz aircraft_dynamics

200 Hz

Vz_control50 Hz

Va_control

50 Hz

altitude_hold50 Hz

h_filter100 Hz

Va_filter

100 Hz

Vz_filter

100 Hz

q_filter

100 Hz

az_filter

100 Hz

h_c

10 Hz

Va_c10 Hz

Controller

Environment simulationT

δ

e

δec

δthc

Vzc

Vz

h

az

q

Va

azf

hf

Vzf

qf

Vaf

Flight condition: h = 10000 m, Va = 230 m/s

- 5 filters consolidate the measured outputs provided by the sensors- 3 controllers track accurately: altitude (hc), vertical speed (Vzc) and airspeed commands (Vac) - rate choices

1. for controllers:- closed-loop system with the continuous-time controller can tolerate a pure time

delay of 1 s before destabilizing → sampling period ≤ 1 Hz- Performances → sampling period ≤ 10 Hz

2. for environment: 200 Hz to model a continuous-time phenomenon



Validation objective (and analysis at Simulink level)

Analysis of Va and Vz loops with separate step demands

Airspeed (Vac) variation of 5 m/s

vertical speed (Vzc)

demand of 2.5m/s




Results for decoupled approach :




Analysis of P4: input is a step climb altitude change of 1000 m- first phase: constant vertical speed demand- second phase: altitude reaching



ROSACE: outline

● Introduction



● Checker


● Perspectives



Python script : check_result.py

https://svn.onera.fr/schedmcore/branches/ROSACE_CaseStudy/checker/

• Goal: verify that a tracing of a given simulation is compliant with the time-domain performance requirements of the previous table

• Input format: CSV (comma separated value) file • 3 property checking:

(1) Decoupled scenarios in Va (2) Decoupled scenario in Vz(3) Step climb

• Possibility to draw the performances• For a new implementation, the user must

(1) Trace exactly the same variables. Which variables must be traced is detailed at the beginning of simulink-run- scenarioX-results.csv.

(2) apply the same input step to the controller. (3) store the simulation (or execution) tracings in a .csv file. (4) call the property checker


https://svn.onera.fr/schedmcore/branches/ROSACE_CaseStudy/checker/


ROSACE: outline

● Introduction



● Checker


● Perspectives



Implementation 1 : “hand-written” Prelude + C



- Identification of performance requirements

- Coding of multi-periodic assembly: Prelude- Analyse several multi-periodic assemblies wrt to the performance requirements and real-time efforts


- A predictable execution model in ZOL- Compliance with the high level requirements



Implementation 1 : “hand-written” Prelude + C

• Coding of the basic blocks • Discretization and manual coding in C• Forward Euler method for the environment• Forward difference for the controllers• Zero-order hold approximation for the filters

• Coding of the assembly in Prelude



Implementation 1 : Prelude in a nutshell

• Prelude: a real-time synchronous language. Allow to express real-time behaviours in a synchronous style• By using relaxed synchronous hypothesis (Curic 2005)

• By adding the notion of real-time periodic clock

• By generating dependent task sets with extended precedence constraints

• By reusing Sofronis et al. communication protocol

• SchedMcore framework (we will see that in part 2)• Simulation of Prelude programs• Script that verifies if a trace fulfils the requirements

A clock α=(ti) is strictly periodic iff∃n N∈ ∗, i N, t∀ ∈ i+1 − ti = n

α)=n is the period, (α)=t0 is the offset.eg: (120, 1/2) is the clock of period 120 and offset 60.

F (10, 5, 10, 0)S (40, 15, 40, 0)F[4k] S[k]S[k] F[4k+4]



Implementation 1 : First Prelude version

node assembly (h_c, Va_c: real rate (1000,0)) returns (delta_e_c, delta_th_c : real)var Va, Vz, q, az, h: real; Va_f, Vz_f, q_f, az_f, h_f : real; Vz_c, delta_e, T : real;let h_f = h_filter(h/^2); Va_f = Va_filter(Va/^2); Vz_f = Vz_filter(Vz/^2); q_f = q_filter(q/^2); az_f = az_filter(az/^2); Vz_c = altitude_hold (h_f/^2, h_c*^5); delta_th_c = Va_control (Va_f/^2, Vz_f/^2, q_f/^2, Va_c*^5); delta_e_c = Vz_control (Vz_f/^2, Vz_c, q_f/^2, az_f/^2); T = engine (delta_th_c*^4); delta_e = elevator (delta_e_c*^4); (Va, Vz, q, az, h)= aircraft_dynamics ((0.018645918123716 fby delta_e), (43219.8575 fby

T));tel

aircraft_dynamics

h_filter

altitude_hold

Vz_control

elevator

Basic clock (1,0) at 100 µs( c o m p l i a n t w i th F i g u r e 3 ) :

N o d e F r e q u e n c y C l o c k N o d e F r e q u e n c y C l o c k

a l t i tu d e _ h o l d 5 0 H z ( 2 0 0 , 0 ) h _ fi l te r 1 0 0 H z ( 1 0 0 , 0 )V a _ fi l te r 1 0 0 H z ( 1 0 0 , 0 ) q _ fi l te r 1 0 0 H z ( 1 0 0 , 0 )a z _ fi l te r 1 0 0 H z ( 1 0 0 , 0 ) V a _ c o n t r o l 5 0 H z ( 2 0 0 , 0 )V z _ c o n t r o l 5 0 H z ( 2 0 0 , 0 ) e n g i n e 2 0 0 H z ( 5 0 , 0 )e l e v a to r 2 0 0 H z ( 5 0 , 0 ) a c _ d y n a m i c s 2 0 0 H z ( 5 0 , 0 )

C . V a r i a t i o n s i n th e a s s e m b l y to r e l a x r e a l - t i m e c o n s tr a i n ts

T h i s fi r s t s p e c i fi c a t i o n i s v e r y c o n s tr a i n e d i n te r m o f r e a l -t i m e a n d th e e f f o r t o f i n te g r a t i o n w i l l b e s t r i n g e n t . I n d e e d , w eh a v e r e d u c e d th e f r e q u e n c i e s b y i m p l e m e n t i n g a m u l t i - p e r i o d i cc o n tr o l l e r i n s te a d o f d e s i g n i n g a m o n o - p e r i o d i c th a t r u n s a t2 0 0 H z . T h i s d e c r e a s e s th e C P U u s a g e b u t th e p r e c e d e n c ec o n s tr a i n ts i m p o s e d b y th e c o m m u n i c a t i o n f o r c e s e v e r a l ta s k sto e x e c u te i n a v e r y s h o r t i n te r v a l . F o r i n s ta n c e , th e f u n c t i o n a lc h a i n h → h f → V z c → δ e c → δ e p r o d u c e s th e e x e c u t i o ns h o w n i n F i g u r e 6 . T h e s e q u e n c e o f ta s k s a i r c r a f t _ d y n a m i c s ,h _ fi l te r , a l t i tu d e _ h o l d , V z _ c o n t r o l , e l e v a to r m u s t e x e c u te i nl e s s th a n 5 m s e v e r y 2 0 m s .

a i r c r a f t _ d y n a m i c s

h _ f i l t e r

a l t i t u d e _ h o l d

V z _ c o n t r o l

e l e v a t o r

F i g u r e 6 . F u n c t i o n a l c h a i n i n th e s p e c i fi c a t i o n

R e l a x i n g p r e c e d e n c e s . T o r e l a x th e e f f o r t o f i n te g r a t i o n , th es e c o n d p r e c e d e n c e p a t te r n s i n F i g u r e 7 a r e b e t te r s u i te d . I n d e e d ,th e s y s te m b e c o m e s m o r e p a r a l l e l i s a b l e a n d / o r W C E T o f ta s k sw i th l o w e r f r e q u e n c y c a n b e i n c r e a s e d . T h e u n i q u e d i f f e r e n c ef o r c o d i n g th e a s s e m b l y i n P R E L U D E ( n a m e d i n th a t c a s ea s s e m b l a g e _ v 2 ) s ta n d s i n th e tw o e q u a t i o n s :T = e n g i n e ( ( 1 . 6 4 0 2 2 2 2 9 6 1 6 2 3 1 6 f b y d e l t a _ t h _ c ) ∗ ^ 4 ) ;d e l t a _ e = e l e v a t o r ( ( 0 . 0 1 8 6 4 5 9 1 8 1 2 3 7 1 6 f b y d e l t a _ e _ c ) ∗ ^ 4 ) ;

N o te th a t p r o d u c i n g th e s a m e b e h a v i o u r i n S I M U L I N K i s r a th e rc o m p l e x . N o te a l s o th a t b r e a k i n g th e d e p e n d e n c i e s i s d o n ew i th th e f b y o p e r a to r , b o r r o w e d f r o m L U C I D S Y N C H R O N E

[ 1 8 ] , th a t d e l a y s a fl o w b y o n e p e r i o d .

h _ f i l t e r


V z _ c o n t r o l

e l e v a t o r

F i g u r e 7 . R e l a x e d f u n c t i o n a l c h a i n

R e l a x i n g p e r i o d s . A s i l l u s tr a te d p r e v i o u s l y , m o d i f y i n g th ea s s e m b l y i s v e r y e a s y i n P R E L U D E . S i n c e i t i s a l s o s i m p l e to

g e n e r a te th e tr a c i n g s , th e c o n tr o l e n g i n e e r c a n e a s i l y v e r i f y i fth e c o n t r o l l e r p e r f o r m a n c e s a r e f u l fi l l e d . T h i s o p e n s th e r o o mf o r te s t i n g m a n y s o l u t i o n s .

I n th i s p a p e r , w e w i l l t r y th r e e m o r e a s s e m b l i e s th a tr e d u c e p e r i o d s a n d p r e c e d e n c e s . N e x t a s s e m b l y ( n a m e d a s s e m -b l a g e _ v 3 ) r e d u c e s s o m e f r e q u e n c i e s : h _ fi l te r , V a _ fi l te r , V z _ fi l te ra r e a t 5 0 H z a n d a l t i tu d e _ h o l d i s a t 1 0 H z . F o r th e th r e e fi l te r s ,w e h a v e to c h a n g e th e r a te o f th e i n p u t fl o w a s f o l l o w s :

h _ f = h _ f i l t e r ( h / ^ 4 ) ;

F o r a l t i tu d e _ h o l d , th e e q u a ti o n b e c o m e sV z _ c = a l t i t u d e _ h o l d ( h _ f / ^ 5 , h _ c ) ;

T h e e q u a t i o n o f V z _ c o n t r o l h a s a l s o to b e m o d i fi e d a s f o l l o w :d e l t a _ e _ c = V z _ c o n t r o l ( V z _ f , V z _ c ∗ ^ 5 , q _ f / ^ 2 , a z _ f / ^ 2 ) ;

I n th i s v e r s i o n , d e p e n d e n c i e s a r e d i r e c t a s i n F i g u r e 6 , w h i l ea s s em b l a g e _ v 4 r e u s e s th o s e o f F i g u r e 7 . I n a s s em b l a g e _ v 4 1 ,w e c h a n g e d th e d e p e n d e n c i e s w h i l e k e e p i n g th e f r e q u e n c i e s .I n a s s em b l a g e _ v 5 , w e p u t V z _ c o n t r o l a n d V a _ c o n t r o l a t 2 5 H z .

D . V a l i d a t i o n o f th e c o d i n g

A l l th e p r e v i o u s a s s e m b l i e s h a v e b e e n s i m u l a te d o n a P Cu s i n g S C H E D M C O R E f r a m e w o r k . T o d o s o , w e r e l y o n th es i m u l a to r l s c m _ r u n - n o r t p r o v i d e d w i th S C H E D M C O R E 5 . T oa s s e s s th e c o r r e c tn e s s o f th e v a r i o u s a s s e m b l i e s , w e c o m p a r e dth e t i m e - r e s p o n s e s to th e s a m e s te p c l i m b s i m u l a te d . F i g u r e 8s u p e r i m p o s e s th e r e s u l t s o f S I M U L I N K ( F i g u r e 5 ) a n d th o s e o fa l l th e a s s e m b l i e s f o r th e s a m e a u to p i l o t i n s t r u c t i o n s . O v e r a l l ,th e r e i s n o s i g n i fi c a n t d e g r a d a t i o n a n d o n l y th e s e t t l i n g t i m ei s s l i g h t l y i m p a c te d b y th e m o d i fi c a t i o n s . I n d e e d , w e p l a y o nth e r a te s a n d p r e c e d e n c e s th a t i m p a c t th e r e s p o n s e - t i m e s b u tn o t th e f u n c t i o n a l v a l u e s ( n o s i g n i fi c a n t i m p a c t o n p r o p e r t i e sP 2 a n d P 3 ) . F i n a l l y , w e o b s e r v e th a t th e c o n tr o l l e r i s r o b u s tto th e r e l a x a t i o n s . S i n c e a l l r e s u l t s a r e s a t i s f y i n g , th e d i f f e r e n ta s s e m b l i e s c a n b e i n te g r a te d o n th e ta r g e t a n d a s s e s s e d a t th i sl e v e l .

I V . E X P E R I M E N T S

T h i s s e c t i o n i l l u s t r a te s th e f e a s i b i l i ty o f i m p l e m e n t i n g th ep a r a l l e l fl i g h t c o n t r o l l e r o n a m u l t i / m a n y - c o r e . T h i s s h o w sth a t th e a b s t r a c t h y p o th e s e s m a d e a t th e S I M U L I N K a n d th eP R E L U D E l e v e l s a r e r e a s o n a b l e . I n p a r t i c u l a r , th e b a s i c c l o c k ,th e r e l a x e d s y n c h r o n o u s h y p o th e s i s a n d th e c o m m u n i c a t i o n p r o -to c o l c a n b e i m p l e m e n te d . W e th e r e f o r e d e s c r i b e i n th i s s e c t i o nth e p o r t i n g o f th e c o d e o n th e T I L E R A T I L E M P O W E R G X - 3 6 .W e i m p o s e a n e x e c u t i o n m o d e l to e n f o r c e p r e d i c ta b i l i ty o n th ep l a t f o r m i n o r d e r to r e s p e c t a s m u c h a s p o s s i b l e th e s a f e tya v i o n i c s ta n d a r d s .

A . T I L E R A d e s c r i p t i o n

T h e p l a t f o r m i s e q u i p p e d w i th a t i l e d m i c r o p r o c e s s o rc o m p o s e d o f 3 6 t i l e s . E a c h t i l e c a n c o m m u n i c a te w i th o th e rt i l e s , th e p e r i p h e r a l s a n d th e e x te r n a l m e m o r y th r o u g h a n e tw o r ko n c h i p ( N o C ) . T h e e x te r n a l m e m o r y i s c o m p o s e d o f 3 2 G B i t s

5 S C H E D M C O R E i s a v a i l a b l e o n th e s v n r e p o s i to r y h t tp s : / / s v n . o n e r a . f r /s c h e d m c o r e / b r a n c h e s / s c h e d m c o r e - R T A S 2 0 1 4

( c o m p l i a n t w i th F i g u r e 3 ) :

N o d e F r e q u e n c y C l o c k N o d e F r e q u e n c y C l o c ka l t i tu d e _ h o l d 5 0 H z ( 2 0 0 , 0 ) h _ fi l te r 1 0 0 H z ( 1 0 0 , 0 )V a _ fi l te r 1 0 0 H z ( 1 0 0 , 0 ) q _ fi l te r 1 0 0 H z ( 1 0 0 , 0 )a z _ fi l t e r 1 0 0 H z ( 1 0 0 , 0 ) V a _ c o n t r o l 5 0 H z ( 2 0 0 , 0 )V z _ c o n t r o l 5 0 H z ( 2 0 0 , 0 ) e n g i n e 2 0 0 H z ( 5 0 , 0 )e l e v a to r 2 0 0 H z ( 5 0 , 0 ) a c _ d y n a m i c s 2 0 0 H z ( 5 0 , 0 )

C . V a r i a t i o n s i n th e a s s em b l y to r e l a x r e a l - t i m e c o n s tr a i n ts

T h i s fi r s t s p e c i fi c a t i o n i s v e r y c o n s tr a i n e d i n te r m o f r e a l -t i m e a n d th e e f f o r t o f i n t e g r a t i o n w i l l b e s t r i n g e n t . I n d e e d , w eh a v e r e d u c e d th e f r e q u e n c i e s b y i m p l e m e n t i n g a m u l t i - p e r i o d i cc o n tr o l l e r i n s te a d o f d e s i g n i n g a m o n o - p e r i o d i c th a t r u n s a t2 0 0 H z . T h i s d e c r e a s e s th e C P U u s a g e b u t th e p r e c e d e n c ec o n s tr a i n ts i m p o s e d b y th e c o m m u n i c a t i o n f o r c e s e v e r a l ta s k sto e x e c u te i n a v e r y s h o r t i n te r v a l . F o r i n s ta n c e , th e f u n c t i o n a lc h a i n h → h f → V z c → δ e c → δ e p r o d u c e s th e e x e c u t i o ns h o w n i n F i g u r e 6 . T h e s e q u e n c e o f ta s k s a i r c r a f t_ d y n a m i c s ,h _ fi l te r , a l t i tu d e _ h o l d , V z _ c o n t r o l , e l e v a to r m u s t e x e c u te i nl e s s th a n 5 m s e v e r y 2 0 m s .

a i r c r a f t _ d y n a m i c s

h _ f i l t e r


V z _ c o n t r o l

e l e v a t o r

F i g u r e 6 . F u n c t i o n a l c h a i n i n th e s p e c i fi c a t i o n

R e l a x i n g p r e c e d e n c e s . T o r e l a x th e e f f o r t o f i n te g r a t i o n , th es e c o n d p r e c e d e n c e p a t te r n s i n F i g u r e 7 a r e b e t te r s u i te d . I n d e e d ,th e s y s te m b e c o m e s m o r e p a r a l l e l i s a b l e a n d / o r W C E T o f ta s k sw i th l o w e r f r e q u e n c y c a n b e i n c r e a s e d . T h e u n i q u e d i f f e r e n c ef o r c o d i n g th e a s s e m b l y i n P R E L U D E ( n a m e d i n th a t c a s ea s s em b l a g e _ v 2 ) s ta n d s i n th e tw o e q u a t i o n s :T = e n g i n e ( ( 1 . 6 4 0 2 2 2 2 9 6 1 6 2 3 1 6 f b y d e l t a _ t h _ c ) ∗ ^ 4 ) ;d e l t a _ e = e l e v a t o r ( ( 0 . 0 1 8 6 4 5 9 1 8 1 2 3 7 1 6 f b y d e l t a _ e _ c ) ∗ ^ 4 ) ;

N o te th a t p r o d u c i n g th e s a m e b e h a v i o u r i n S I M U L I N K i s r a th e rc o m p l e x . N o te a l s o th a t b r e a k i n g th e d e p e n d e n c i e s i s d o n ew i th th e f b y o p e r a to r , b o r r o w e d f r o m L U C I D S Y N C H R O N E

[ 1 8 ] , th a t d e l a y s a fl o w b y o n e p e r i o d .

h _ f i l t e r


V z _ c o n t r o l

e l e v a t o r

F i g u r e 7 . R e l a x e d f u n c t i o n a l c h a i n

R e l a x i n g p e r i o d s . A s i l l u s t r a te d p r e v i o u s l y , m o d i f y i n g th ea s s e m b l y i s v e r y e a s y i n P R E L U D E . S i n c e i t i s a l s o s i m p l e to

g e n e r a te th e t r a c i n g s , th e c o n tr o l e n g i n e e r c a n e a s i l y v e r i f y i fth e c o n tr o l l e r p e r f o r m a n c e s a r e f u l fi l l e d . T h i s o p e n s th e r o o mf o r te s t i n g m a n y s o l u t i o n s .

I n th i s p a p e r , w e w i l l t r y th r e e m o r e a s s e m b l i e s th a tr e d u c e p e r i o d s a n d p r e c e d e n c e s . N e x t a s s e m b l y ( n a m e d a s s e m -b l a g e _ v 3 ) r e d u c e s s o m e f r e q u e n c i e s : h _ fi l te r , V a _ fi l te r , V z _ fi l te ra r e a t 5 0 H z a n d a l t i tu d e _ h o l d i s a t 1 0 H z . F o r th e th r e e fi l te r s ,w e h a v e to c h a n g e th e r a te o f th e i n p u t fl o w a s f o l l o w s :

h _ f = h _ f i l t e r ( h / ^ 4 ) ;

F o r a l t i tu d e _ h o l d , th e e q u a t i o n b e c o m e sV z _ c = a l t i t u d e _ h o l d ( h _ f / ^ 5 , h _ c ) ;

T h e e q u a t i o n o f V z _ c o n tr o l h a s a l s o to b e m o d i fi e d a s f o l l o w :d e l t a _ e _ c = V z _ c o n t r o l ( V z _ f , V z _ c ∗ ^ 5 , q _ f / ^ 2 , a z _ f / ^ 2 ) ;

I n th i s v e r s i o n , d e p e n d e n c i e s a r e d i r e c t a s i n F i g u r e 6 , w h i l ea s s em b l a g e _ v 4 r e u s e s th o s e o f F i g u r e 7 . I n a s s e m b l a g e _ v 4 1 ,w e c h a n g e d th e d e p e n d e n c i e s w h i l e k e e p i n g th e f r e q u e n c i e s .I n a s s e m b l a g e _ v 5 , w e p u t V z _ c o n t r o l a n d V a _ c o n t r o l a t 2 5 H z .

D . V a l i d a t i o n o f th e c o d i n g

A l l th e p r e v i o u s a s s e m b l i e s h a v e b e e n s i m u l a te d o n a P Cu s i n g S C H E D M C O R E f r a m e w o r k . T o d o s o , w e r e l y o n th es i m u l a to r l s c m _ r u n - n o r t p r o v i d e d w i th S C H E D M C O R E 5 . T oa s s e s s th e c o r r e c tn e s s o f th e v a r i o u s a s s e m b l i e s , w e c o m p a r e dth e t i m e - r e s p o n s e s to th e s a m e s te p c l i m b s i m u l a te d . F i g u r e 8s u p e r i m p o s e s th e r e s u l t s o f S I M U L I N K ( F i g u r e 5 ) a n d th o s e o fa l l th e a s s e m b l i e s f o r th e s a m e a u to p i l o t i n s t r u c t i o n s . O v e r a l l ,th e r e i s n o s i g n i fi c a n t d e g r a d a t i o n a n d o n l y th e s e t t l i n g t i m ei s s l i g h t l y i m p a c te d b y th e m o d i fi c a t i o n s . I n d e e d , w e p l a y o nth e r a te s a n d p r e c e d e n c e s th a t i m p a c t th e r e s p o n s e - t i m e s b u tn o t th e f u n c t i o n a l v a l u e s ( n o s i g n i fi c a n t i m p a c t o n p r o p e r t i e sP 2 a n d P 3 ) . F i n a l l y , w e o b s e r v e th a t th e c o n tr o l l e r i s r o b u s tto th e r e l a x a t i o n s . S i n c e a l l r e s u l t s a r e s a t i s f y i n g , th e d i f f e r e n ta s s e m b l i e s c a n b e i n t e g r a te d o n th e ta r g e t a n d a s s e s s e d a t th i sl e v e l .

I V . E X P E R I M E N T S

T h i s s e c t i o n i l l u s t r a te s th e f e a s i b i l i t y o f i m p l e m e n t i n g th ep a r a l l e l fl i g h t c o n tr o l l e r o n a m u l t i / m a n y - c o r e . T h i s s h o w sth a t th e a b s tr a c t h y p o th e s e s m a d e a t th e S I M U L I N K a n d th eP R E L U D E l e v e l s a r e r e a s o n a b l e . I n p a r t i c u l a r , th e b a s i c c l o c k ,th e r e l a x e d s y n c h r o n o u s h y p o t h e s i s a n d th e c o m m u n i c a t i o n p r o -to c o l c a n b e i m p l e m e n te d . W e th e r e f o r e d e s c r i b e i n th i s s e c t i o nth e p o r t i n g o f th e c o d e o n th e T I L E R A T I L E M P O W E R G X - 3 6 .W e i m p o s e a n e x e c u t i o n m o d e l to e n f o r c e p r e d i c ta b i l i t y o n th ep l a t f o r m i n o r d e r to r e s p e c t a s m u c h a s p o s s i b l e th e s a f e tya v i o n i c s ta n d a r d s .

A . T I L E R A d e s c r i p t i o n

T h e p l a t f o r m i s e q u i p p e d w i th a t i l e d m i c r o p r o c e s s o rc o m p o s e d o f 3 6 t i l e s . E a c h t i l e c a n c o m m u n i c a te w i th o th e rt i l e s , th e p e r i p h e r a l s a n d th e e x te r n a l m e m o r y th r o u g h a n e tw o r ko n c h i p ( N o C ) . T h e e x te r n a l m e m o r y i s c o m p o s e d o f 3 2 G B i ts

5 S C H E D M C O R E i s a v a i l a b l e o n th e s v n r e p o s i to r y h t tp s : / / s v n . o n e r a . f r /s c h e d m c o r e / b r a n c h e s / s c h e d m c o r e - R T A S 2 0 1 4



Implementation 1 : Other Prelude coding

T = engine ((1.640222296162316 fby delta_th_c)*^4);delta_e = elevator ((0.018645918123716 fby delta_e_c)*^4);

h_filter

altitude_hold

Vz_control

elevator

aircraft_dynamics

h_f = h_filter(h/^4);Va_f = Va_filter(Va/^4);Vz_f = Vz_filter(Vz/^4); Vz_c = altitude_hold (h_f/^5, h_c); delta_th_c = Va_control (Va_f, Vz_f, q_f/^2, Va_c*^5); delta_e_c = Vz_control (Vz_f, Vz_c*^5, q_f/^2, az_f/^2);

• Relaxing precedences:

• Relaxing periods, h_filter, Va_filter, Vz_filter at 50Hz; altitude_hold at 10Hz:



Implementation 1 : Functional Simulation

• Objective: • Simulation of the specification• Real-time constraints are

assumed correct• Input:

• Prelude program• Code of imported nodes

• Results• no significant degradation and

only the settling time is slightly impacted by the modifications.



On the Tilera Gx36 target

Timing issues•local time-stamp counter•cores start independently => unpredictable offsets

36 tiles– Single core clocked at 1.2 GHz– 32 KB program memory (L1P)– 32 KB data memory (L1D)– 256 KB level 2 memory (L2)

NoC (network on chip)- five full-duplex sub-networks- Shared Dynamic Network (SDN) for

exchanging data between tiles, e.g., for cache coherency

- reQuest Dynamic Network (QDN) for write requests to the DDR

- Response Dynamic (RDN) Network for read requests to the DDR

Development environment- Zero Overhead Linux (ZOL): no non-

user interrupts- Shared memory with cache homing

policy



Predictable rules for the Tilera

• Stressing benchmarks to assess the variability of the platform• impact on the execution times when several tiles access concurrently the

shared resources (read and write), such as DDR, local caches and NoC.• time to access the local clock

• Mapping rules1.No more than 10 tiles must simultaneously access in writing the same

[shared] cached memory location 2.No more than 5 tiles must simultaneously access in writing the DDR3.No more than 30 tiles must simultaneously access in reading the same

[shared] cached memory location4.Offline partitioned non preemptive schedule5.Memory footprint fits in the local caches

Puffitsch W., Noulard E. and Pagetti C., Off-Line Mapping of Multi-Rate Dependent Task Sets to Many-Core Platforms, Real-Time Systems, September 2015, Volume 51, Issue 5, pp 526-565http://dx.doi.org/10.1007/s11241-015-9232-1

Find better and general rules in :


http://dx.doi.org/10.1007/s11241-015-9232-1


Mapping the flight controller on the Tilera 1/2

• WCET in isolation

• offline mapping (manual computation)• One -core to one task

Tile 1

Tile 2

Tile 3

200µs

300µs 500µs 700µs

800µs

Aircraft_dynamics

h_filter az_filter Vz_filter q_filter Va_filter

altitude_hold Vz_control Va_control

elevator engine



Mapping the flight controller on the Tilera 2/2

• Tick-based scheduling • Decisions taken only at discrete instants

• Communication delay on the NoC

• Clock precision

→ Enforce WCET

Puffitsch W., Noulard E. and Pagetti C., Off-Line Mapping of Multi-Rate Dependent Task Sets to Many-Core Platforms, Real-Time Systems, September 2015, Volume 51, Issue 5, pp 526-565http://dx.doi.org/10.1007/s11241-015-9232-1

W. Puffitsch, E. Noulard, and C. Pagetti, “Mapping a multi-rate synchronous language to a many-core processor,” in 19th IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS 2013), 2013, pp. 293–302.


http://dx.doi.org/10.1007/s11241-015-9232-1


Tilera execution results

• Objective: • Run on the Tilera• WCET extended with tick gap

• Input:• Prelude program• Code of imported nodes• Mapping rules

• Results• Almost the same as those

obtained by the functional ones



Implementation 1 on Tilera : summary



- Identification of performance requirements

- Coding of multi-periodic assembly: Prelude- Analyse several multi-periodic assemblies wrt to the performance requirements and real-time efforts


- A predictable execution model in ZOL- Compliance with the high level requirements

• Design of a parallel avionic longitudinal controller on a multi/many-core target• Illustration of discussion between control engineers and integrators can be

leveraged, in order to find a compromise between both sides constraints.



Implementation 2 : “Generated” Prelude + Lustre



SchedMcoreSchedMcore

node voter (s1, s2, s3: real)returns (sensor: real);let : : :tel Imported node voter ((s1, s2, s3: real)

returns (sensor: real) wcet 5;node ex (i1 : rate(8,0); i2 : rate(20,0)) returns (01, 02);let : : :tel

ONERA Sim2LustrePrelude toolbox (Matlab) – open source – on demandGenerator coming soon at : https://forge.onera.fr/projects/sim2preludelustre

See generated implementation in ROSACE:https://svn.onera.fr/schedmcore/branches/ROSACE_CaseStudy/prelude_implementations/prelude_lustre/


https://forge.onera.fr/projects/sim2preludelustre

https://svn.onera.fr/schedmcore/branches/ROSACE_CaseStudy/prelude_implementations/prelude_lustre/


Perspective : the big picture



Perspectives: Use ROSACE ! Go ahead it’s open !!

• Go to the ROSACE page on SchedMCore site


• Use the provided implementation and try your own

• Do no hesitate to report bugs or propose contribution/alternate implementation on the forge of the project:

https://forge.onera.fr/projects/rosace-case-study



https://forge.onera.fr/projects/rosace-case-study


Questions?


real-time scheduling on multi/many-processor: from...

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