Modern CPU architectures provide a large number of processing cores and application programmers are increasingly looking at hybrid programming models, where multiple threads of a single process interact with the MPI library simultaneously. Moreover, recent high-speed interconnection networks are being designed with capabilities targeting communication explicitly from multiple processor cores. As a result, scalability of the MPI library so that multithreaded applications can efficiently drive independent network communication has become a major concern. In this work, we propose a novel operating system level concept called the thread private shared library (TPSL), which enables threads of a multithreaded application to see specific shared libraries in a private fashion. Contrary to address spaces in traditional operating systems, where threads of a single process refer to the exact same set of virtual to physical mappings, our technique relies on per-thread separate page tables. Mappi...