1. A processing system, comprising: a plurality of processor cores; a control register comprising a plurality of inhibit bits, each inhibit bit indicating whether a corresponding processor core is allowed to merge with other processor cores; and dynamic core reallocation logic to temporarily merge a first processor core and a second processor core to speed execution of a first thread executed on the first processor core responsive to determining that a second thread executed on the second processor core has completed execution prior to a quantum associated with the second thread being reached and to determining that the inhibit bits indicate that the first and second cores may be merged.