Refining SIRAP with a dedicated resource ceiling for self-blocking

In recent years, several synchronization protocols for resource sharing have been presented for use in a Hierarchical Scheduling Framework (HSF). An initial comparative assessment of existing protocols revealed that none of the protocols is superior to the others and that the performance of a protocol heavily depends on system parameters. In this paper, we aim at efficiency improvements of the synchronization protocol SIRAP [5] and its associated schedulability analysis, where efficiency refers to calculated CPU resource needs. The contribution of the paper is threefold. Firstly, we present an improvement of the schedulability analysis for SIRAP, which makes SIRAP more efficient. Secondly, we generalize SIRAP by distinguishing separate resource ceilings for self-blocking and resource access. Using a separate resource ceiling for self-blocking enables a reduction of the interference from lower priority tasks, which can result in efficiency improvements. The efficiency improvement depends on both subsystem characteristics and the value selected for the resource ceiling for self-blocking, however. The third contribution of this paper is therefore an algorithm that given a subsystem selects for each globally shared resource an optimal value in terms of efficiency for its resource ceiling for self-blocking. The efficiency improvement gained by the algorithm compared to the original SIRAP approach is evaluated by means of simulation.