All processes with dynamic priorities are handled by the CFS class, and as most processes in general-purpose *nix systems are normal (non-realtime), CFS remains the busiest scheduler class in the kernel.

CFS relies on maintaining balance in allocating processor time to tasks, based on policies and dynamic priorities assigned per task. Process scheduling under CFS is implemented under the premise that it has an "ideal, precise multi-tasking CPU," that equally powers all processes at its peak capacity. For instance, if there are two processes, the perfectly multi-tasking CPU ensures that both processes run simultaneously, each utilizing 50% of its power. As this is practically impossible (achieving parallelism), CFS allocates processor time to a process by maintaining proper balance across all contending processes. If a process fails to receive a fair amount of time, it is considered out of balance, and thus goes in next as the best runnable process.

CFS...