Abstract: In this research, we describe the functionality of AGAS (Active Global Address Space), a subsystem of the HPX runtime system that is designed to handle data locality at runtime, independent of the hardware and architecture configuration. AGAS enables transparent runtime global data access and data migration, but incurs a an overhead cost at runtime. We present a method to assess the performance of AGAS and the amount of impact it has on the execution time of the Octo-Tiger application. With our assessment method we identify the four most expensive AGAS operations in HPX and demonstrate that the overhead caused by AGAS is negligible.