A method, system, and program are provided for managing execution of mixed workloads in a simultaneous multi-threaded (SMT) enabled system. In one embodiment, in a SMT enabled processor system, having multiple processors each activated to interleave execution of multiple hardware threads on each processor, for ST workload, the kernel of the SMT enabled processor system facilitates construction of an exclusive set of processors to simulate an ST mode for handling the tasks of the ST workload, wherein the ST workload runs more efficiently on single threaded processors. The kernel schedules the ST workload on the exclusive set of processors by selecting one hardware thread per processor within said exclusive set of processors to handle a separate one of the tasks of the ST workload, while requiring the remaining hardware threads per processor within the exclusive set to idle. As a result, the ST workload is executed on the SMT enabled processor system as if the exclusive set of processors run in ST mode, but without actually deactivating the remaining idle hardware threads per processor within the exclusive set of processors.