Task response time for real-time distributed systems with resource contentions

An analytic model is proposed for estimating task response times in distributed systems with resource contentions. The model consists of two submodels. The first submodel is an extended queuing network model used for approximating module response times. This submodel is solved by a decomposition technique which reduces the computational complexity by two to three orders of magnitude when compared with a direct approach. The second submodel is a weighted control-flow graph model from which task response time can be obtained by aggregating module response time in accordance with the precedence relationships. Task response times estimated by the analytic model compare closely with simulation results. It is shown that resource contention delays depend on the availability of resources as well as on the invocation rates and response times of the modules that use the resources. The model can be used to study the tradeoffs among module assignments, scheduling policies, interprocessor communications, and resource contentions in distributed processing systems