This paper generalizes the load scaling techniques proposed in [7, 8] by relating the criticality and flexibility of a process to the resource allocation problem. We propose a framework for adjusting the system workload when the timing parameters of processes may change in reaction to the environment. When the list of allowable configurations is implicitly given by scalable periodic processes, the corresponding weighted period assignment problem is shown to be NP-complete. We present an approximation algorithm for the period assignment problem and show some very encouraging results.