Modeling reentrant and nonreentrant software

A description of software module models for computer systems is presented. The software module models are based on a two level description, the software level and the hardware level, of the computer system. In the software module level it is possible to model performance effects of software traits such as reentrant and nonreentrant type software modules. The resulting queueing network models are, in general, not of the product form class and approximation schemes are employed as solution techniques. An example of a software module model of a hypothetical computer system is presented. The model is solved with a simulation program and three approximation schemes. The approximation results were compared with the simulation results and some schemes are found to produce good estimates of the effects of changing from reentrant to non-reentrant software modules.