Software Performability Model with Two Kinds of Restoration

摘要

本論文では，実時間性を考慮したソフトウェアの性能評価法について考察する．ソフトウェアの動的振舞いはマルコフ過程により記述される．このとき，運用段階で実施される2種類の修復作業を考慮する．1つはデバッグ作業を伴う修復作業で，もう1つはデバッグ作業を伴わない修復作業である．システムの形態としては，複数の仕事を同時に処理するマルチタスクシステムを想定し，仕事の到着過程を非同次ポアソン過程で記述し，各仕事に課される処理時間制約を確率変数として取り扱う．到着した仕事のうち処理が完了できる仕事数の分布は，無限サーバ待ち行列モデルの考え方を用いて解析する．本モデルに基づいて，ソフトウェアの性能評価尺度を．時間およびデバッグ回数の関数として導出する．最後に，導出された性能評価尺度の数値例を示し，仕事の多様性や運用指向の修復作業の考慮が性能評価結果に与える影響について考察する．%In this paper, we discuss software performability evaluation considering the real-time property. The time-dependent behavior of the system alternating between up and down state is described by the Markov process. Then we incorporate the operation-oriented restoration scenario into the model, i.e., we consider the following two types of restoration: one is the restoration with debugging and the other is without debugging. Assuming that the software system can process the multiple tasks simultaneously, we also consider the variety of tasks in terms of the task arrival process and the processing time limit. We describe the arrival process of the tasks follows a nonhomoge-neous Poisson process and treat the processing time limit as a random variable. 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. From the model, we derive several software performability measures considering the real-time property. Finally, we illustrate several numerical examples of the measures to investigate the impact of the variety of tasks and the operational restoration on the system performability evaluation.