In multi-channel wireless mesh networks (WMNs), the routing and channel assignment can interdependently determine network capacity. However, Joint Routing and Channel assignment (JRC) is a challenging problem since it must satisfy the Radio Constraint, the Channel Constraint, and the Co-channel Interference Constraint. Recently, many heuristic or suboptimization algorithms have been proposed to address the JRC problem. The aim of this paper is to preform a comprehensive performance study to fairly compare the different approaches. To achieve this goal, a proper benchmark, a Mixed Integer Linear Programming (MILP) model that can optimally configure the routing and channel assignment to get maximum achievable network capacity, is provided in this work as well. The proposed MILP model can help system designers quantitatively evaluate existing heuristic methods and make a better decision by considering the tradeoff between the characteristics of various schemes according to the system requirements.