1. Software Dynamics: A New Method of Evaluating Real-Time Performance of Distributed Systems Janusz Zalewski Computer Science Florida Gulf Coast University Ft. Myers, FL 33965-6565 http://www.fgcu.edu/zalewski/ FALSE2002, Nashville, Nov. 14-15, 2002

2. Talk Outline RT Software Architecture Evaluating S/W Architectures Timeliness & S/W Dynamics Conclusion FALSE2002, Nashville, Nov. 14-15, 2002

3. Feedback Control System FALSE2002, Nashville, Nov. 14-15, 2002

4. Generic Real-Time Software Architecture FALSE2002, Nashville, Nov. 14-15, 2002

5. Sensor/Actuator component User Interface component Communication Link component Database component Processing component Timing component. Basic Components of Real-Time Software Architecture FALSE2002, Nashville, Nov. 14-15, 2002

6. Air-Traffic Control System Physical Diagram FALSE2002, Nashville, Nov. 14-15, 2002

7. Air-Traffic Control System Context Diagram FALSE2002, Nashville, Nov. 14-15, 2002

8. The idea of grouping I/O information into different categories, which later determine the software architecture follows the fundamental software engineering principle of separation of concerns (Parnas, 1970s). FALSE2002, Nashville, Nov. 14-15, 2002

9. Model of a Distributed Embedded Simulation FALSE2002, Nashville, Nov. 14-15, 2002

10. We are missing good (any) measures to characterize Behavioral Properties of a software module (its dynamics). FALSE2002, Nashville, Nov. 14-15, 2002

11. Interrupt Latency The time interval between the occurrence of an external event and start of the first instruction of the interrupt service routine. FALSE2002, Nashville, Nov. 14-15, 2002

12. H/W logic processing Interrupt disable time Handling higher H/W priorities Switching to handler code. Interrupt Latency Involves FALSE2002, Nashville, Nov. 14-15, 2002

13. Real-Time System Responsiveness FALSE2002, Nashville, Nov. 14-15, 2002

14. Dispatch Latency The time interval between the end of the interrupt handler code and the first instruction of the process activated (made runnable) by this interrupt. FALSE2002, Nashville, Nov. 14-15, 2002

15. Dispatch Latency Involves OS decision time to reschedule (non-preemptive kernel state) context switch time return from OS call. FALSE2002, Nashville, Nov. 14-15, 2002

16. Real-Time Properties * Responsiveness * Timeliness * Schedulability * Predictability FALSE2002, Nashville, Nov. 14-15, 2002

17. How to measure these properties? * Responsiveness - just outlined * Timeliness - proposed below * Schedulability - rate monotonic and deadline monotonic analyses. FALSE2002, Nashville, Nov. 14-15, 2002

18. Two measures of timeliness: * Overall time deadlines are missed (by a task) * Number of times deadlines are missed by X percent FALSE2002, Nashville, Nov. 14-15, 2002

19. 5-task Benchmark FALSE2002, Nashville, Nov. 14-15, 2002

20. Overall time the deadlines are missed for 100 experiments. FALSE2002, Nashville, Nov. 14-15, 2002

21. The number of times the deadlines are missed by 2%.

22. Overall time the deadlines are missed for 100 experiments (CORBA). FALSE2002, Nashville, Nov. 14-15, 2002

23. The number of times the deadlines are missed by 2% (CORBA). FALSE2002, Nashville, Nov. 14-15, 2002

24. ATCS: Software Components Communicating via CORBA FALSE2002, Nashville, Nov. 14-15, 2002

25. Overall time (in milliseconds) deadlines are missed for 20 aircraft (in 100 experiments). FALSE2002, Nashville, Nov. 14-15, 2002

26. Number of times deadlines are missed by more than 20% for 20 aircraft (in 100 experiments). FALSE2002, Nashville, Nov. 14-15, 2002

29. Satellite Ground Control Station FALSE2002, Nashville, Nov. 14-15, 2002

30. SGCS Implementation FALSE2002, Nashville, Nov. 14-15, 2002

31. SGCS Physical Architecture FALSE2002, Nashville, Nov. 14-15, 2002

33. Single DB Client Request Processing Time. FALSE2002, Nashville, Nov. 14-15, 2002

34. Percent of deadlines missed for one DB Client. FALSE2002, Nashville, Nov. 14-15, 2002

35. Five DB Clients Request Processing Time. FALSE2002, Nashville, Nov. 14-15, 2002

36. Percent of deadlines missed for five DB Clients. FALSE2002, Nashville, Nov. 14-15, 2002

37. Sensitivity: a measure of the magnitude of system’s response to changes. FALSE2002, Nashville, Nov. 14-15, 2002

38. Sensitivity: (y1 – y0)/[(y1 + y0)/2] (x1 – x0)/[(x1 + x0)/2] FALSE2002, Nashville, Nov. 14-15, 2002

39. Sensitivity = 1.73 FALSE2002, Nashville, Nov. 14-15, 2002

40. Sensitivity = 1.00 FALSE2002, Nashville, Nov. 14-15, 2002

41. Sensitivity = 1.64 FALSE2002, Nashville, Nov. 14-15, 2002

42. First Order Dynamics G(s) = K / (  *s + 1) FALSE2002, Nashville, Nov. 14-15, 2002

43. Time constant -  : a measure of the speed of system’s response to changes. FALSE2002, Nashville, Nov. 14-15, 2002

44. Settling Time: time when curve reaches 2% max Time Constant = 0.25 * Settling Time FALSE2002, Nashville, Nov. 14-15, 2002

45.  = 165 ms FALSE2002, Nashville, Nov. 14-15, 2002

46.  = 87.5 ms FALSE2002, Nashville, Nov. 14-15, 2002

47.  = 15 ms FALSE2002, Nashville, Nov. 14-15, 2002

48. Distributed Embedded Simulation Architecture FALSE2002, Nashville, Nov. 14-15, 2002

49. Statistical measures of timeliness: * Round-trip time stability * Service time effect FALSE2002, Nashville, Nov. 14-15, 2002

50. Service time effect for a specific architecture FALSE2002, Nashville, Nov. 14-15, 2002

51. Round-trip message time for 5-task simulation FALSE2002, Nashville, Nov. 14-15, 2002

52. Conclusion Behavioral Properties are crucial for successful software development Sensitivity is one important property Software Dynamics seems to be a measurable property as well FALSE2002, Nashville, Nov. 14-15, 2002