A mainframe computing system includes a central processor complex, a plurality of billing entities, each billing entity having a respective capacity limit, and a workload manager that schedules work requested by the plurality of billing entities on the central processor complex and tracks, by billing entity, a rolling average of millions of service units. The mainframe also includes a dynamic capping policy that identifies a maximum MSU limit, a maximum cost limit, a subset of the plurality of billing entities, and, for each billing entity in the subset, information from which to determine a MSU entitlement value and cost entitlement value. The mainframe also includes a dynamic capping master that adjusts the respective capacity limits of the subset of the plurality of billing entities at scheduled intervals based on the dynamic capping policy to favor billing entities having high-importance workload within the maximum MSU limit and maximum cost limit.