System dynamics is an approach to understanding the behaviour of complex systems over time. It deals with internal feedback loops and time delays that affect the behaviour of the entire system. What makes using system dynamics different from other approaches to studying complex systems is the use of feedback loops and stocks and flows“.

In this article we should how this maps extremely nicely to concepts in QoS in particular services which are classified flows and resources are stocks. We then show how using services/flows and resources/stocks we can model and control the execution dynamics of an instrumented software in terms of concurrency (thread stock) and consumption (call stock).