Real-Time Analysis of Servers for General Job Arrivals

Several servers have been proposed to schedule streams of a periodic jobs in the presence of other periodic tasks. Standard schedulability analysis has been extended to consider such servers. However, not much attention has been laid on computing the worst-case delay suffered by a given stream of jobs when scheduled via a server. Such analysis is essential for using servers to schedule hard real-time tasks. We illustrate, with examples, that well established resource models, such as supply bound function and models from Real-Time Calculus, do not tightly characterize servers. In this work, we analyze the server algorithm of the Constant Bandwidth Server and compute a provably tight resource model of the server. The approach used enables us to differentiate between the soft and hard variants of the server. A similar approach can be used to characterize other servers, the final results for which are presented.