New results on fixed priority aperiodic servers

The issue of using the sporadic server (SS) for scheduling aperiodic tasks has received new attention under the POSIX standard as it has been proposed in P1003.1 d, the additional real-time extensions to POSIX. The SS has been traditionally considered a better approach to the deferrable server (DS) due to its supposed higher achievable utilisation. However, SS also has higher implementation complexity. Nevertheless, the analysis of the comparisons performed from several authors between DS and SS is not conclusive. A review on fixed priority servers is presented with a new parameter selection technique and comprehensive performance analysis based on simulation techniques. With this parameter selection, it is shown that no server performs significantly better than the other in most of the situations. This suggests that future POSIX revisions for real-time support should also consider mechanisms by which other types of servers could be implemented.