An earlier time for inserting and/or accelerating tasks

In a periodic real-time system scheduled by the EDF (Earliest Deadline First) algorithm (Liu and Layland, J. ACM 20(1), 40–61, 1973; Barauh, Proc. of the 27th IEEE International Real-Time Systems Symposium, 379–387, 2006; Buttazzo, J. Real-Time Syst. 29(1), 5–26, 2005), when new tasks have to be inserted into the system at run-time and/or current tasks request to increase their rates in response to internal or external events, the new sum of the utilizations after the insertion and/or acceleration should be limited, otherwise, one or more current tasks should usually be compressed (their periods being prolonged) in order to avoid overload. Buttazzo offered a time from which on this kind of adjustment can be done without causing any deadline miss in the system (Buttazzo et al., IEEE Trans. Comput. 51(3), 289–302, 2002). It is, however, not early enough. In this paper, an earlier time is given and formally proved.

Qian GuangmingEmail: