A first performance measurement of an executing task may be determined, while the task is executed by a first number of nodes operating in parallel. A second performance measurement of the executing task may be determined, while the task is being executed by a second number of nodes operating in parallel. An overhead factor characterizing a change of a parallelism overhead of executing the task with nodes executing in parallel may then be calculated, relative to a change in a number of the nodes, based on the first performance measurement and the second performance measurement. Then, an optimal number of nodes to operate in parallel to continue executing the task may be determined, based on the overhead factor.