Scheduling and Memory requirements analysis with AADL

1

• Scheduling and Memory requirements analysis with
  AADL
• F. Singhoff, J. Legrand, L. Nana, L. Marcé
• University of Brest, France
• LISYC/EA 3883

2
Introduction and motivations (1/2)

• The Architecture Analysis Design Language
  (AADL)
• SAE standard published in november 2004 (AS 5506
  document).
• Allows a high level specification of real time
  systems in order to perform analysis, source
  code/documentation generation,
• An AADL specification is
• A set of components such as
• Thread flow of control that executes a program
  (eg. Ada Task).
• Data any data structure in a program (eg. Ada
  tagged record).
• Processor part of the execution environment.
• Connections between components model component
  relationships.
• Component properties component
  information/characteristic (behavior, Ada
  package file name, Ada task stack requirement,
  )

3
Introduction and motivations (2/2)

• Existing AADL toolsets OSATE, STOOD, TOPCASED,
  ADeS but there is currently few open-source
  performance analysis tools.
• Since 2002, at Brest, were investigating
• How to extend real time system analysis methods
  to take distribution into account ?
• How to provide tools to help system designers to
  predict distributed real time system performances
  ?
• Cheddar, an Ada framework designed to real time
  applications performance analysis.
• How Cheddar can be applied to AADL
  specifications ?

4
Talk overview

• Introduction and project motivations
• Usual performance analysis methods
• Cheddar a performance analyzer framework
• Examples of AADL analysis
• AADL threads scheduling analysis
• AADL event data port memory analysis
• Conclusion and ongoing works

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Usual performance analysis methods real time
scheduling (1/2)

• Periodic task model a bound on execution time
  (capacity, Ci), a fixed delay between two wake-up
  times (period,Pi), a temporal constraint to meet
  (deadline, Di).
• Choose a real time scheduling algorithms (eg.
  Rate Monotonic).
• Perform simulation analysis compute and analyze
  time lines
• Perform Analytical/Feasibility test analysis
  no scheduling required

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Usual performance analysis methods queueing
systems (2/2)

• Queueing system Kendall's notation X/Y/n.
• X customer arrival rate (M,G,D).
• Y service time rate (M,G,D).
• n number of servers.
• Examples M/M/1, M/D/1, M/G/1,
• Goal From a given customer arrival/service time
  rate, compute analytical criteria such as
  customer waiting time and number of waiting
  customers in the queue.

7
Talk overview

• Introduction and project motivations
• Usual performance analysis methods
• Cheddar a performance analyzer framework
• Examples of AADL analysis
• AADL threads scheduling analysis
• AADL event data port memory analysis
• Conclusion and ongoing works

8
Cheddar a performance analyzer framework
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Cheddar and AADL
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Talk overview

• Introduction and project motivations
• Usual performance analysis methods
• Cheddar a performance analyzer framework
• Examples of AADL analysis
• AADL threads scheduling analysis
• AADL event data port memory analysis
• Conclusion and ongoing works

11
AADL threads scheduling analysis (1/3)

• AADL includes most of the features used in the
  context of real time scheduling analysis.
• Nevertheless, the following questions have to be
  investigated
• Can we model any built-in Cheddar's schedulers or
  task models ?
• Are standard properties enough to perform
  analytical/feasibility tests on any resources ?
• How to express new schedulers or task models ?

gt we need some new AADL properties related to
thread, data and processor
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AADL threads scheduling analysis (2/3)

• Example a set of periodic/aperiodic threads
  scheduled with POSIX1003.1b and Rate Monotonic
  schedulers.

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AADL threads scheduling analysis (3/3)
Compute simulation
14
Talk overview

• Introduction and project motivations
• Usual performance analysis methods
• Cheddar a performance analyzer framework
• Examples of AADL analysis
• AADL threads scheduling analysis
• AADL event data port memory analysis
• Conclusion and ongoing works

15
Event data ports memory requirement analysis
(1/4)

• Event data ports are AADL features used for
  asynchronous message transmission between
  threads. Events/messages are queued.
• Queueing systems may be able to predict event
  data port me mory requirement .... But we have to
  answer two questions
• How to take into account AADL thread dispatching
  (eg. periodic) ?
• How to take into account AADL thread scheduling
  (eg. RM) ?
• As for the other AADL features, Cheddar provides
  
• Simulation tools.
• Feasibility tests (based on queueing systems, J.
  Legrand, F. Singhoff, L. Nana L. Marcé 2004).

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Event data ports memory requirement analysis
(2/4)

• Queueing systems for AADL event data ports
• Define a new customer arrival/service time rate
  the P rate.
• Define new queueing systems based on the P rate.
• Define new feasibility tests.
• Worst case analytical analysis based on P/P/1
• Consumer/Producer threads are periodic.
• Ex. Feasibility test the maximum number of
  messages in an event data port shared by N
  periodic producers and 1 periodic consumer is
• 2.N (harmonic AADL thread set)
• 2.N1 (other cases)
• Average case analytical analysis based on M/P/1
• See the SIGAda 2005 proceedings for the
  feasibility tests.

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Event data ports memory requirement analysis
(3/4)

• Example 2 event data port
• connections

thread Producer Features Data_Source out
event data port end Producer thread Consumer
features Data_Sink in event data port end
Consumer thread implementation Producer.i
properties Dispatch_ProtocolgtPeriodic ... e
nd Producer.i thread implementation Consumer.i
properties Dispatch_ProtocolgtPer
iodic ... end Consumer.i
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Event data ports memory requirement analysis
(4/4)
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Talk overview

• Introduction and project motivations
• Usual performance analysis methods
• Cheddar a performance analyzer framework
• Examples of AADL analysis
• AADL threads scheduling analysis
• AADL event data port memory analysis
• Conclusion and ongoing works

20
Conclusion and ongoing works

• The Cheddar AADL performance analyzer
• Provides performance analysis tools for different
  AADL features, based on real time scheduling and
  queueing systems analysis.
• This AADL analyzer is distributed since the end
  of october (http//beru.univ-brest.fr/singhoff/ch
  eddar) ... but has to be tested !
• Implementation based on Ocarina (ENSTs AADL Ada
  95 parser).
• Cheddar can be run as a Stood plug-in, the
  TNI-Europe CASE tool (Thanks to AADL !).
• Ongoing works
• Related to thread precedency relationships (AADL
  connections).
• Related to hierarchical schedulers (eg. ARINC 653
  scheduler).