Availability-Based Software Performability Model with User-Perceived Performance Degradation

This paper discusses software performability evaluation considering the real-time property. We assume that the software system has two operational states from the viewpoint of the end users: one is operating with the desirable performance level according to specification and the other is with degraded performance level. The time-dependent behavior of the system is described by the Markovian software availability model with performance degradation. Assuming that the system can process the multiple tasks simultaneously, we analyze the distribution of the number of tasks whose processes can be completed within the processing time limit with the infinite server queueing model. We derive several software performability measures; these are given as the functions of time and the number of debugging activities. Finally, we illustrate several numerical examples of the measures to investigate the impact of consideration of the performance degradation on the system performability evaluation.