Methods and apparatus provide for a workload adjuster to estimate the startup cost of one or more non-main threads of loop execution and to estimate the amount of workload to be migrated between different threads. Upon deciding to parallelize the execution of a loop, the workload adjuster creates a scheduling policy with a workload for a main thread and workloads for respective non-main threads. The scheduling policy distributes iterations of a parallelized loop to the workload of the main thread and iterations of the parallelized loop to the workloads of the non-main threads. The workload adjuster evaluates a start-up cost of the workload of a non-main thread and, based on the start-up cost, migrates a portion of the workload for that non-main thread to the main thread's workload.