A synchronous scheduling service for distributed real-time Java
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  • 1. A synchronous scheduling service (SSS) for distributed real-time Java Pablo Basanta-Val, Iria Estévez-Ayres, Marisol García-Valls, and Luis Almeida mailto:pbasanta@it.uc3m.es†Jornadas de Tiempo Real 2011- Madrid( ) Publicado en IEEE Transactions on Parallel and Distributed Systems
  • 2. Outline• Context and Motivation• FTT and DREQUIEMI integration• SSS (Synchronous Scheduling Service) – Master Slave Model – Choreographies – Choreographies scheduling/scheduler – Architecture and examples – Performance• Conclusion and ongoing work 2
  • 3. Context• Java programmers may use two specifications for develop their real-time applications – RTSJ: The Real-Time Specification for Java – DRTSJ: The Distributed Real-Time Specification for Java• DRTSJ has focused on remote object upcalling and abstractions (distributable threads). – But not in a predictable networks – Networks predictability is a requirement JRT-11 3
  • 4. In this work• We introduce time-triggered orientation in distributed real-time Java – Basic model used the FTT (Flexible Time-Triggered) protocol – Supported as a new service in distributed real-time Java • SSS (Synchronous Scheduling Service)• We obtain a more predictable network management – Useful for instance in high-integrity applications JRT-11 4
  • 5. FTT and DREQUIEMIintegration (1/3) JRT-11 5
  • 6. FTT and DREQUIEMIintegration (2/3) JRT-11 6
  • 7. FTT and DREQUIEMIintegration (3/3) JRT-11 7
  • 8. System overview JRT-11 8
  • 9. Choreographies set JRT-11 9
  • 10. T and S choreographies JRT-11 10
  • 11. C and P choreographies JRT-11 11
  • 12. SchedulingChoreographies• Each choreography is modeled as non preemptive task – {O, T, C, D}• The choreographies executed by the master - It runs a NPR-EDF- Simple admission control (T=D) JRT-11 12
  • 13. Implementation issues:Convergence Layer JRT-11 13
  • 14. Example 1: real-timeproducer consumer (1/2) Every 10 ms Maximum Process data generates a network delay: coming from a sample 20 ms producer 10 10 producer consumer slave slave JRT-11 14
  • 15. Example real-timeproducer consumer (2/2) Every 10 ms Maximum network Process data generates a sample delay: coming from a 20 ms producer 10 10 producer consumer slave slave PC# Produce# producer # CC.data O= 5ms master T= 10 ms C= 2 ms D= 10 ms NPR-EDF CC # Consume# consumer# O= 15 ms T= 10 ms C= 2 ms D= 10 ms JRT-11 15
  • 16. Experiments (1/2) Master-slave templatesEnd-to-End costs (us) Convergence Layerover 796 MHz-100Mbps DREQUIEMI J2ME-RMIOP JTime TimesysOs JRT-11 16
  • 17. Experiments (2/2) Master-slave templatesEnd-to-End costs (bytes) Convergence Layerover 796 MHz-100Mbps DREQUIEMI J2ME-RMIOP JTime TimesysOs
  • 18. Master-slaveJitter [new] templates Convergencetime vs. event triggered Layer DREQUIEMI J2ME-RMIOP JTime TimesysOs JRT-11 18
  • 19. Conclusions• Developed techniques to include time-triggered orientation in distributed real-time Java – Synchronous Scheduling Service (SSS)• Empirical evidences showed better performance than an ET approach – Because TCP/IP stacks and OS are not fully preemptive JRT-11 19
  • 20. Ongoing work• Developing a minimum time-triggered implementation without DREQUIEMI – Ongoing master thesis• Changes in the model – NPR-RMS model vs. NPR-EDF – One way choreographies JRT-11 20
  • 21. JRT-11 21