Software contention aware queueing network model of three-tier web systems

Using modelling to predict the performance characteristics of software applications typically uses Queueing Network Models representing the various system hardware resources. Leaving out the software resources, such as the limited number of threads, in such models leads to a reduced prediction accuracy. Accounting for Software Contention is a challenging task as existing techniques to model software components are complex and require deep knowledge of the software architecture. Furthermore, they also require complex measurement processes to obtain the model's service demands. In addition, solving the resultant model usually require simulation solvers which are often time consuming. In this work, we aim to provide a simpler model for three-tier web software systems which accounts for Software Contention that can be solved by time efficient analytical solvers. We achieve this by expanding the existing "Two-Level Iterative Queuing Modelling of Software Contention" method to handle the number of threads at the Application Server tier and the number of Data Sources at the Database Server tier. This is done in a generic manner to allow for extending the solution to other software components like memory and critical sections. Initial results show that our technique clearly outperforms existing techniques.