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FALSE2002, Nashville, Nov. 14-15, 2002. Software D y namic s: 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/.

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Software D y namic s: A New Method of Evaluating Real-Time Performance of Distributed Systems

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Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

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/


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Talk Outline

  • RT Software Architecture

  • Evaluating S/W Architectures

  • Timeliness & S/W Dynamics

  • Conclusion


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Feedback Control System


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Generic Real-Time

Software Architecture


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Basic Components of Real-TimeSoftware Architecture

  • Sensor/Actuator component

  • User Interface component

  • Communication Link component

  • Database component

  • Processing component

  • Timing component.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Air-Traffic Control System

Physical Diagram


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Air-Traffic Control System

Context Diagram


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

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).


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Model of a Distributed

Embedded Simulation


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

We are missing good (any) measures to characterize Behavioral Properties of a software module (its dynamics).


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Interrupt Latency

The time interval between the occurrence of an external event and start of the first instruction of the interrupt service routine.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Interrupt Latency Involves

  • H/W logic processing

  • Interrupt disable time

  • Handling higher H/W priorities

  • Switching to handler code.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Real-Time System

Responsiveness


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

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.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Dispatch Latency Involves

  • OS decision time to reschedule (non-preemptive kernel state)

  • context switch time

  • return from OS call.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Real-Time Properties

* Responsiveness

* Timeliness

* Schedulability

* Predictability


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

How to measure these properties?* Responsiveness - just outlined* Timeliness - proposed below* Schedulability - rate monotonic and deadline monotonic analyses.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Two measures of timeliness:* Overall time deadlines are missed (by a task)* Number of times deadlines are missed by X percent


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

5-task Benchmark


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Overall time the deadlines are missed for 100 experiments.


Software d y namic s a new method of evaluating real time performance of distributed systems

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


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Overall time the deadlines are missed for 100 experiments (CORBA).


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

The number of times the deadlines are missed by 2% (CORBA).


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

ATCS: Software Components

Communicating via CORBA


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Overall time (in milliseconds) deadlines are missed for 20 aircraft (in 100 experiments).


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Number of times deadlines are missed by more than 20% for 20 aircraft (in 100 experiments).


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Satellite Ground Control Station


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

SGCS Implementation


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

SGCS Physical Architecture


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Single DB Client Request Processing Time.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Percent of deadlines missed for one DB Client.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Five DB Clients Request Processing Time.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Percent of deadlines missed for five DB Clients.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Sensitivity:a measure of the magnitude of system’s response to changes.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Sensitivity:(y1 – y0)/[(y1 + y0)/2] (x1 – x0)/[(x1 + x0)/2]


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Sensitivity = 1.73


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Sensitivity = 1.00


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Sensitivity = 1.64


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

First Order Dynamics G(s) = K / (t*s + 1)


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Time constant - t:a measure of the speed of system’s response to changes.


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

  • Settling Time:

  • time when curve reaches 2% max

  • Time Constant = 0.25 * Settling Time


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

t = 165 ms


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

t = 87.5 ms


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

t = 15 ms


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Distributed Embedded Simulation Architecture


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Statistical measures of timeliness: * Round-trip time stability * Service time effect


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Service time effect for a specific architecture


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Round-trip message time for 5-task simulation


Software d y namic s a new method of evaluating real time performance of distributed systems

FALSE2002, Nashville, Nov. 14-15, 2002

Conclusion

  • Behavioral Properties are crucial for successful software development

  • Sensitivity is one important property

  • Software Dynamics seems to be a measurable property as well


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