  We define a pi-calculus variant with a costed semantics where channels are
treated as resources that must explicitly be allocated before they are used and
can be deallocated when no longer required. We use a substructural type system
tracking permission transfer to construct coinductive proof techniques for
comparing behaviour and resource usage efficiency of concurrent processes. We
establish full abstraction results between our coinductive definitions and a
contextual behavioural preorder describing a notion of process efficiency
w.r.t. its management of resources. We also justify these definitions and
respective proof techniques through numerous examples and a case study
comparing two concurrent implementations of an extensible buffer.
