D11: a High-performance, Protocol-optional, Transport-optional Window System with X11 Compatibility and Semantics

Consider the dual pressures toward a more tightly integrated workstation window system: 1) the need to eeciently handle high bandwidth services such as video, audio, and three-dimensional graphics; and 2) the desire to achieve the under-realized potential for local window system performance in X11. This paper proposes a new window system architecture called D11 that seeks higher performance while preserving compatibility with the industry-standard X11 window system. D11 reinvents the X11 client/server architecture using a new operating system facility similar in concept to the Unix kernel's traditional implementation but designed for user-level execution. This new architecture allows local D11 programs to execute within the D11 window system kernel without compromising the window system's integrity. This scheme minimizes context switching, eliminates protocol packing and unpacking, and greatly reduces data copying. D11 programs fall back to the X11 protocol when running remote or connecting to an X11 server. A special D11 program acts as an X11 protocol translator to allow X11 programs to utilize a D11 window system.