The notion of resource plays a central role in concurrent systems. In its purest form a resource is simply a unique identity one can create, use and ultimately destruct. In this paper we propose a simple yet effective characterization of resource usages and develop for it a complete analysis framework. We address qualitative issues such as the classification of resources and whether two systems exhibit similar patterns of resource usages -- namely equivalent resource profiles. From the quantitative point of view, we develop the omniscient garbage collector (OGC), which decides precisely when a resource can be reclaimed or reused. This allows to bound precisely the number of resources consumed by a given system. To illustrate the approach, we study experimentally the resource consumption of pi-calculus processes using a prototype analysis tool. We propose two different resource abstractions for pi-processes: one based on the labelled transitions for open systems, and another one for closed systems. The latter notably provides a refined view of behaviors, less opaque than reductions. Beyond this experiment, the proposed framework is quite generic and can apply to many different formalisms and situations.