Processor preallocation and load balancing of DOALL loops

Load balance is important because it may affect the speedup attained through the concurrent execution of loop iterations on a parallel processor. We study loop load balance in the context of the well-known Perfect benchmarks. Several static and dynamic characteristics of the Perfect benchmark DOALL loops are observed and interpreted. The late arrival of processors is noted as a major source of load imbalance. This observation suggested the idea of processor preallocation. An analytic cost model is presented and the advantages of processor preallocation are demonstrated by experimental evaluation on a CRAY Y-MP8 under the Unicos operating system.