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Modern high-performance networks offer remote direct memory access (RDMA) that exposes a process' virtual address space to other processes in the network. The Message Passing Interface (MPI) specification has recently been extended with a programming interface called MPI-3 Remote Memory Access (MPI-3 RMA) for efficiently exploiting state-of-the-art RDMA features. MPI-3 RMA enables a powerful programming model that alleviates many message passing downsides. In this work, we design and develop bufferless protocols that demonstrate how to implement this interface and support scaling to millions of cores with negligible memory consumption while providing highest performance and minimal overheads. To arm programmers, we provide a spectrum of performance models for RMA functions that enable rigorous mathematical analysis of application performance and facilitate the development of codes that solve given tasks within specified time and energy budgets. We validate the usability of our library and models with several application studies with up to half a million processes. In a wider sense, our work illustrates how to use RMA principles to accelerate computation- and dataintensive codes. [ABSTRACT FROM AUTHOR]