Abstract. BlueGene/L is a massively parallel cellular architecture system with a toroidal interconnect. Cellular architectures with a toroidal interconnect are effective at producing highly scalable computing systems, but typically require job partitions to be both rectangular and contiguous. These restrictions introduce fragmentation issues that affect the utilization of the system and the wait time and slowdown of queued jobs. We propose to solve these problems for the BlueGene/L system through scheduling algorithms that augment a baseline first come first serve (FCFS) scheduler. Restricting ourselves to space-sharing techniques, which constitute a simpler solution to the requirements of cellular computing, we present simulation results for migration and backfilling techniques on BlueGene/L. These techniques are explored individually and jointly to determine their impact on the system. Our results demonstrate that migration can be effective for a pure FCFS scheduler but that backfilling produces even more benefits. We also show that migration can be combined with backfilling to produce more opportunities to better utilize a parallel machine.