Scheduling policies that make their scheduling decisions during runtime are classified as online schedulers.
These schedulers make their scheduling decisions online based on the system’s timing constraints, such as task priority.
Schedulers that base their scheduling decisions on task priorities are called priority-driven schedulers.
Priority-driven scheduling policies can be divided into fixed-priority schedulers (FPSs) and dynamic-priority schedulers (DPSs).
The difference between these scheduling policies is whether the priorities of the real-time tasks are fixed or whether they can change during execution (i.e., dynamic priorities).