Design and Implementation of the UVM Virtual Memory System

We introduce UVM, a new virtual memory subsystem for 4.4BSD that makes better use of existing hardware memory management features to reduce overhead and improve performance. Our novel approach focuses on allowing processes to pass memory to and from other processes and the kernel, and to share memory. This approach reduces or eliminates the need to copy data thus reducing the time spent within the kernel and freeing up cycles for application processing. Unlike the approaches that focus exclusively on the networking and inter-process communications (IPC) subsystems, our approach provides a general framework for solutions that can improve efficiency of the entire I/O subsystem. Our primary objective in creating UVM was to produce a virtual memory system that provides a Unix-like operating system kernel's I/O and IPC subsystems with ef..