TABLE OF CONTENTS Once we have decided to perform an assessment of performance for some target computer system, we still must decide which of the techniques we have discussed is the most appropriate for the proposed performance study. Many different considerations must be taken into account before we make such a decision.
The four techniques for computer systems performance evaluation include analytical modeling, Petri net modeling, simulation modeling, and empirical or testbed analysis. Depending on the criteria placed on the computer systems analysis, some rough selection metrics can be determined. The most important criterion deals with the stage of the computer systems life cycle. For example, measurements are only available as a modeling possibility if the system already exists, or something similar exists. On the other hand, if it is a new computer system, which has not been built, then analytical modeling, Petri nets, or simulation modeling makes more sense. If we are in the earliest phases of the life cycle, when we are examining tradeoffs on many components, we may wish to use analytical modeling, since it can provide relatively quick answers to tradeoff questions, allowing us to determine early on if a subset of n alternatives is best for more detailed modeling. Once we have completed this rough analysis, and narrowed our choices of alternatives to some smaller subset, we would probably wish to apply Petri nets to further refine our choices. Petri nets add the ability to model and trade off concurrency, conflict, and synchronization, something...
