The Earliest Deadline First (EDF) scheme executes the thread closest to its deadline. Therefore, the only necessary parameter for this scheme is the deadline. [11] and [15] show, that for periodic threads on a single processor system this is an optimal scheme. It guarantees all deadlines up to 100% processor utilization.
The Least Laxity First (LLF) scheme can be considered as an extension to the Earliest Deadline First scheme. Additionally to the deadline, the execution time of each thread is used to calculate its laxity. The laxity is the difference between the remaining time to the deadline and the remaining execution time of a thread. The thread with the least laxity gets the processor.
Guaranteed Percentage (GP) [6] is a scheme that has been newly designed for real-time scheduling on multithreaded processors. It aims to implement a scheduler for hard real-time requirements simply in hardware. The basic idea is to statically assign percentages of the available processor time to the threads and to guarantee these percentages in short time intervals. This ensures a definite and predictable proceeding of the threads solving the problem of isolation of event-handling threads against each other. A thread cannot harm the timing behavior of any other thread. Such an isolation is important, if dynamic reconfigurability is needed. Threads can be removed or replaced without affecting the behavior of the remaining threads in the system. So real-time constraints can be kept even during reconfiguration.