The Erlang RunTime System (ERTS) is a complex system with many interdependent components. It is written in a very portable way so that it can run on anything from a gum stick computer to the largest multicore system with terabytes of memory. In order to be able to optimize the performance of such a system for your application, you need to not only know your application, but you also need to have a thorough understanding of ERTS itself.