Abstract: A system and method for performing backfilling on an incoming flow of incoming parallel programs provided by a population of clients to a facility, the system comprising a computer-controlled prediction functionality operative to generate a current run-time prediction for at least some of the incoming parallel programs, a backfiller performing backfilling on the incoming flow of incoming parallel programs based at least partly on at least some of the run-time predictions; and a prediction updater operative, if the current run-time of an incoming parallel program currently in process exceeds the current run-time prediction, to generate an updated run-time prediction to exceed the current run-time, to re-define the current run time to equal the updated run-time prediction, thereby to allow the backfiller to continue performing backfilling based on the updated run-time prediction.