Selective buddy allocation for scheduling parallel jobs on clusters

In this paper we evaluate the performance implications of using a buddy scheme for contiguous node allocation, in conjunction with a backfilling job scheduler for clusters. When a contiguous node allocation strategy is used, there is a trade-off between improved run-time of jobs (due to reduced link contention and lower communication overhead) and increased wait-time of jobs (due to external fragmentation of the processor system). Using trace-based simulation, a buddy strategy for contiguous node allocation is shown to be unattractive compared to the standard noncontiguous allocation strategy used in all production job schedulers. A simple but effective scheme for selective buddy allocation is then proposed, that is shown to perform better than non-contiguous allocation.