Embodiments include method, systems and computer program products for operating a computer system using a workload manager to control a dynamic thread mode switch. The method includes receiving a plurality of workloads. A workload manager determines which of the plurality of workloads are eligible to use a processor core operating in a multi-threaded mode and which workloads are response sensitive and use a processor core operating in a single-thread mode. A hypervisor determines a state of operation for one or more cores of one or more processors and causes a core switch for at least one or more cores in response to a determination that workloads eligible to use a processor core operating in a multi-threaded mode exist or workloads that are response sensitive and a determination that the state of operation for one or more cores of one or more processors should change to facilitate handling the associated workloads.