The X server is charged with providing window system services to many applications simultaneously, and needs a scheduling mechanism to distribute it's limited resources among these applications. The original scheduling mechanism was simplistic and caused graphics-intensive applications to starve interactive applications.
A new scheduling mechanism has been designed which fairly distributes time among the requesting applications while at the same time increasing performance by a small amount. Descriptions of the original and new scheduling mechanism and empirical measurements demonstrating the effects of scheduling within the X server are included along with a discussion on how the design was arrived at.
Usenix Technical Conference 2000
X version 11 was originally designed and implemented in 1987. In the intervening 13 years, there have been advancements in both applications and hardware, but the core of the X Window System has remained largely unchanged. The last major X server architecture changes were included in X11R4. The last wide-spread functional enhancement exported by the X server might well be the Shape extension, designed (in the hot tub) at the 1989 Winter Usenix in San Diego. The rise of inexpensive Unix desktop systems in the last couple of years has led to the development of new user-interface libraries, which are not well served by the existing X rendering model. A new 2D rendering model is being developed to serve this new community of applications. The problem space and proposed solutions are discussed.
Usenix Technical Conference 2000