1. A method for scheduling a new thread, comprising: identifying, by a hardware processor, a criticality level of the new thread; selecting, by the hardware processor, a processor group from a plurality of processor groups according to the criticality level of the new thread and an existing assigned utilization level of the processor group to obtain a selected processor group; increasing an assigned utilization level of the selected processor group based on the new thread; and executing the new thread by the selected processor group.