A method and system are provided for performing efficient and effective scheduling in a multi-threaded system. Dynamic control of scheduling is provided, in which priority weights can be assigned for some or all of the threads in the multi-threaded system. The priority weights are employed to control prioritization of threads and thread instructions by a scheduler. An instruction count for each thread is used in combination with the priority weights to determine the prioritization order in which instructions are fetched and assigned to execution units for processing.