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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A New Method of Evaluating Real-Time
Performance of Distributed Systems
Florida Gulf Coast University
Ft. Myers, FL 33965-6565
Feedback Control System
Basic Components of Real-TimeSoftware Architecture
Air-Traffic Control System
Air-Traffic Control System
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).
Model of a Distributed
We are missing good (any) measures to characterize Behavioral Properties of a software module (its dynamics).
The time interval between the occurrence of an external event and start of the first instruction of the interrupt service routine.
Interrupt Latency Involves
The time interval between the end of the interrupt handler code and the first instruction of the process activated (made runnable) by this interrupt.
Dispatch Latency Involves
How to measure these properties?* Responsiveness - just outlined* Timeliness - proposed below* Schedulability - rate monotonic and deadline monotonic analyses.
Two measures of timeliness:* Overall time deadlines are missed (by a task)* Number of times deadlines are missed by X percent
Overall time the deadlines are missed for 100 experiments.
Overall time the deadlines are missed for 100 experiments (CORBA).
The number of times the deadlines are missed by 2% (CORBA).
ATCS: Software Components
Communicating via CORBA
Overall time (in milliseconds) deadlines are missed for 20 aircraft (in 100 experiments).
Number of times deadlines are missed by more than 20% for 20 aircraft (in 100 experiments).
Satellite Ground Control Station
SGCS Physical Architecture
Single DB Client Request Processing Time.
Percent of deadlines missed for one DB Client.
Five DB Clients Request Processing Time.
Percent of deadlines missed for five DB Clients.
Sensitivity:a measure of the magnitude of system’s response to changes.
Sensitivity:(y1 – y0)/[(y1 + y0)/2] (x1 – x0)/[(x1 + x0)/2]
Sensitivity = 1.73
Sensitivity = 1.00
Sensitivity = 1.64
First Order Dynamics G(s) = K / (t*s + 1)
Time constant - t:a measure of the speed of system’s response to changes.
t = 165 ms
t = 87.5 ms
t = 15 ms
Distributed Embedded Simulation Architecture
Statistical measures of timeliness: * Round-trip time stability * Service time effect
Service time effect for a specific architecture
Round-trip message time for 5-task simulation