Modern operating systems have been designed around the hypotheses that (a) memory is both byte-addressable and volatile and (b) storage is block addressable and persistent. The arrival of new Persistent Memory (PM) technologies, has made these assumptions obsolete. Despite much of the recent work in this space, the need for consistently sharing PM data across multiple applications remains an urgent, unsolved problem. The Region System is a high-performance operating system stack for PM that implements usable consistency and persistence for application data. The region system provides support for consistently mapping and sharing data resident in PM across user application address spaces. Its high-performance design minimizes the expensive PM ordering and durability operations by embracing a minimalistic approach to metadata construction and management. Finally, the region system creates a novel IPI based PMSYNC operation, which ensures atomic persistence of mapped pages across multiple address spaces.