Abstract: The traditional performance analysis of real-time systems relied on the input variable of worst-case execution time， which turned to be too pessimistic.Aiming at the problem of remarkably redundant design in real-time， a new model to characterize variable workload was created including workload curves， inverse workload curves and workload ratio curves. In the proposed model， event type， number and distribution were used as decision-variable， and relevant algorithm was proposed to solve the above model. In addition， the realistic applications were analyzed in mix scheduling based on VWM (variable workload model). The result indicates that the VWM can remarkably reduce execution workload of tasks， thus reducing the resource requirement of real-time systems.

Key words: variable workload model, real-time system, formal method, workload curve, worst-case execution time