According to KernalTrap, here, CFS models an 'ideal, precise multi-tasking CPU' on real hardware. It runs a task with the 'gravest need' for more CPU time and tries to split up CPU time between runnable tasks as close to 'ideal multitasking hardware' as possible.
It will replace Ingo's own O(1) scheduler which was first proposed on January 3rd, 2002 and merged into the 2.5.2-pre10 kernel a few days later. µ