The complexity of node architectures in supercomputers increases as we cross petaflop milestones on the way towards Exascale. Increasing levels of parallelism in multi- and many-core chips and emerging heterogeneity of computational resources coupled with energy and memory constraints force a reevaluation of our approaches towards operating systems and runtime environments. The International Workshop on Runtime and Operating Systems for Supercomputers provides a forum for researchers to exchange ideas and discuss research questions that are relevant to upcoming supercomputers.