In the Software Defined Network (SDN) ecosystem, the controller remains the cornerstone of the architecture and the critical point of its success. That is why performance concerns have existed throughout the history of SDN and controller development. This paper aims at making a reality check on the current performance achieved by mainstream open source controllers. The measurements are carried out in a controlled environment, where each controller is tested with its own opti- mized configuration, on the one hand allowing measuring peak performance, while, on the other hand allowing obtaining fair and reproducible results. Furthermore, besides optimizing the controller configuration, the system wide settings have been also tuned so as to maximize performance. From this comprehensive evaluation, advice on selecting and deploying controllers in real scenarios is derived.