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  • 1. 2013 Jornadas de Tiempo Real de España Valencia, 31 enero-1 Febrero 2013Fine tuning and evaluationof multiplexing facilitiesin Java’s RemoteMethod Invocation* P. Basanta-Val, M. García-Valls, I. Estévez-Ayres , J. González-Fernándezhttp://www.it.uc3m.es/drequiemiUniversidad Carlos III de Madrid* Published in Concurrency and Computation: Practice and Experience (IF:0,6)
  • 2. Outlined presentation • Context and motivation – Efficient multiplexation in Java’s RMI • Background on JRMP and Java´s RMI – Stream – SingleOp – Multiplex • Approach – ConnectionLess • Empirical Results – Bandwidth, response-time, footprint, and latency Valencia, JTR 2013 2
  • 3. Context• Benefits of Java – Reduced development time, automatic memory management, syntax• Real-time Java as of today • RTSJ (Real-Time Specification for Java) – Implementations ready for development • SCJ (Safety Critical Java) • DRTSJ (Distributed Real-Time Java) – no implementations or specifications• Distributed real-time Java requires – End-to-end programming abstractions – Predicable end-to-end resource management • Memory, CPU and Network Valencia, JTR 2013 3
  • 4. The contribution• An efficient multiplexing protocol for RMI – For JRMP(Java’s Remote Method Protocol) – Idea: ConnectionLess subprotocol for JRMP • To allow multiple threads invoke the same remote node “in parallel” and “efficiently”, without penalties – Advance: • Flexibility Only one TCP-IP connection required per each client-server pair !! – Drawback • Constant overhead in communications• Related work: – Some researchers proposed to add new JRMP headers to JRMP (York, JSR-50, UPM, UC3M) in order to produce a RT-JRMP protocol Valencia, JTR 2013 4
  • 5. ConnectionLess as a transport subprotocolfor distributed real-time Java • JRMP default protocol – Stream • Other optional subprotocols – SingleOp – StreamOp • Proposed approach – ConnectionLess Valencia, JTR 2013 5
  • 6. RemoteThe three JRMP Objectsubprotocols and the StubConnectionLess Stub TCP/IP Client VM Server VM Valencia, JTR 2013 6
  • 7. Background on JRMP• Described as “wired protocol” in the Java’s RMI specification• Subprotocols – SingleOp – Stream – Multiplex• Messages – DGCAck – CALL – RETURN – PING – PINGAck Valencia, JTR 2013 7
  • 8. Remote Invocation for SingleOp• They always involved a TCP/IP connection – Very inefficient !! Valencia, JTR 2013 8
  • 9. Remote Invocation with Stream • It may reuse an negotiated stream subconnection for further2013 Valencia, JTR sequential invocations 9
  • 10. Remote Invocation with Multiplex• It allows multiple remote invocations “in parallel” from the same client• However, it is very inefficient – Three negotiations (TCP, RMI connection, Multiplex connection) – Multiple copies to buffers Valencia, JTR 2013 10
  • 11. Remote Invocation with ConnectionLess • Based on Stream and Mux: – VCs managed dynamically by the client • Allows efficient remote invocations in parallel Valencia, JTR 2013 11
  • 12. Supporting ConnectionLess • At JRMP protocol messaging level: – Protocol definition with 0x60 – A new VC(2 bytes) header Valencia, JTR 2013 12
  • 13. Supporting ConnectionLessVC management • The VC used in RETURN is equal to the VC used in CALL • VCs are – generated in order – Reused after the remote invocation Valencia, JTR 2013 13
  • 14. Implementation• Based on RTSJ-RI by TimeSys – Compliant with RTSJ 1.0.2• RMI-OP for J2ME – Supports Stream• (We) added implementation for – SingleOp – Multiplex – ConnectionLess Class diagram for ConnectionLess implementation Valencia, JTR 2013 14
  • 15. Evaluation• Features • Local or remote configuration Traffic Traffic • 1300 Mhz machines x 2 generator generator • 100Mbits SW-Ethernet client server connection RMI_OP RMI_OP• Evaluation metric (stream, singleop, ..) (stream, singleop, ..) – Response-time – Memory RTSJ RTSJ – Bandwidth – Footprint Traffic Analizer Valencia, JTR 2013 15
  • 16. End-to-End Response timeMinimal application payload Valencia, JTR 2013 16
  • 17. End-to-End ResponsetimeWith appl. payload• Trends – SingleOp is the worst protocol – Stream is the best• ConectionLess is the second Valencia, JTR 2013 17
  • 18. End-to-End Response timeWith appl. payload• Stream is the worst protocol• ConnectionLess is the best protocol Valencia, JTR 2013 18
  • 19. Bandwidth results Valencia, JTR 2013 19
  • 20. Bandwidth results• In permanent regime – Stream is the best in perforamnce – ConnectionLess is the second• For concurrent invocations – Connectionless is the best in perfomance Valencia, JTR 2013 20
  • 21. Memory Allocation Results(bytes in Heap) Valencia, JTR 2013 21
  • 22. Memory Allocation Results(bytes in Heap)• In permanent regime – Stream is the best protocol – ConnectionLess is the third !!! • It uses preallocation Valencia, JTR 2013 22
  • 23. Memory Allocation Results(bytes in Heap)• In concurrent invocations – Multiplex is the best in dynamic memory consumption metrics – ConnectionLess is the one with less footprint Valencia, JTR 2013 23
  • 24. Conclusions and ongoing work• This work evaluated a new JRMP subprotocol (ConnectionLess) for parallel remote invocations – Results are satisfactory • Low overhead & parallel invocation supported via VCs• Ongoing work – Impact on control applications – Serialization impact on JRMP communications – Integration of RT-JRMP with ConnectionLess Valencia, JTR 2013 24
  • 25. 2013 Jornadas de Tiempo RealValencia, 31 enero-1 Febrero 2013 Valencia, JTR 2013

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