Fetch operations are assigned to different threads in a multithreaded environment. There are provided a number of different sorting algorithms, from which one is periodically selected on the basis of whether the present algorithm is giving satisfactory results or not. The period is preferably a sub-context interval. The different sorting algorithms preferably include a software/OS priority. A second sorting algorithm may include sorting according to hardware performance measurements. Two-level priority scheme is used to combine both priorities. The judgement of satisfactory performance is preferably based on the difference between a desired number of fetch operations attributed per sub-context switch interval to each thread and a real number of fetch operations attributed per sub-context switch interval to each thread.