The kernel's completely fair scheduler (CFS) has the job of managing the allocation of CPU time for most of the processes running on most Linux systems. CFS was merged for the 2.6.23 release in 2007 and has, with numerous ongoing tweaks, handled the job reasonably well ever since. CFS is not perfect, though, and there are some situations it does not handle as well as it should. The EEVDF scheduler, posted by Peter Zijlstra, offers the possibility of improving on CFS while reducing its dependence on often-fragile heuristics.