On distributed real-time scheduling in networked embedded systems in the presence of Crash failures

Abstract

We consider the problem of scheduling distributable realtime threads in networked embedded systems that operate under runtime uncertainties including those on thread execution times, thread arrivals, and node failure occurrences. We present a distributed scheduling algorithm called CUA. We show that CUA satisfies thread time constraints in the presence of crash failures, is early-deciding, has an efficient message complexity of O(fn) (where f is the number of crashes that actually occur and n is the number of nodes), and is time-optimal with a time lower bound of O(D + fd + nk) (where D is the message delay upper bound, d is the failure detection bound, and k is the maximum number of threads). In crash-free runs, the algorithm constructs schedules within O(D + nk), and yields optimal total utility if nodes are also not overloaded. The algorithm is also "best-effort" in that a high importance thread that may arrive at any time has a very high likelihood for feasible completion (in contrast to classical admission control algorithms which favor feasible completion of admitted threads over admitting new ones, irrespective of thread importance). © IFIP International Federation for Information Processing 2007.