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Gosling: If I Designed a Window System Today...
An anonymous reader writes "In his blog entry for the 10th August, James Gosling (finally) publishes a short paper he wrote in 2002 entitled 'Window System Design: If I had to do it over again in 2002'. His design is to make the window system do the absolute minimum and move all the work into the client."
As Gosling mentions, X is moving in this direction today. In a year or two, when the newest X changes are stable, the average GTK+ or Qt app will talk to the server via OpenGL. On most DRI-like setups, the route from GL to GPU looks like:
OpenGL -> userspace command buffer -> graphics memory (DMA via Direct Rendering Manager).
Text layout, fonts, etc, are all done server-side, and the only thing the "server" sees are pixmaps and GL commands.
A deep unwavering belief is a sure sign you're missing something...
Curiously, the Mac OS X window system implements almost the exact design Jim Gosling describes in his paper.
All drawing work is done on the client side, and the window server has nothing to do with fonts, cut/paste support or much other higher level work. The window server simply assembles the drawing buffers to the displays (via hardware or software) and routes events, using hints of the foreground application and the visible window area to manage the task.
A consistent look and feel is derived by providing a consistent set of high level toolkits, residing on a set of lower level drawing frameworks.
Shared libraries make sure the needed code is readily available and resident in memory. Font are cached and vended as shared memory resources using Mach's virtual memory semantics. Drawing buffers also leverage Mach VM semantics.
The problem is that there isn't enough RAM to preload all the applications. My PC during the day will run (and this is a typical work day) Word, Excel, Outlook, Visio, Project, Firefox, Internet Explorer, and an assortment of programs that don't concern me like virus scanners.
If all of these applications tried to preload themselves on startup then your swap would grind itself into dust and boottime would be in excess of 30 minutes.
It's false reasoning to say that Word takes only 2 seconds. It takes 2 seconds plus whatever time it added to the boot sequence. And if the first application you run isn't Word then there is a good chance that the preloaded Word will be swapped to disk anyway, making the next instance of Word take significantly longer than 2 seconds.
Take note that Mozilla also uses the preload trick. My work machine has consumed all 256MB of RAM and 450MB of swap after a fresh reboot and a login. That's 450MB of intensive swap activity that slowed down my boot sequence. If I just want to check my appointments in Outlook then why am I forced to wait for Word and Mozilla to fight over the swap? It's ludicrous.