Incorporating job sizes in distributed load balancing

The load index most frequently used for load balancing in distributed systems is the job queue length. This work examines some of the implications of scheduling jobs according to an additional abstract dimension attribute called job size. The load balancing algorithm is supported by a virtual ring structure which organises the network nodes in groups and defines the information-gathering activities to take place within and between such groups. A two-phase approach to information gathering and decision making is adopted. This enables the selection of jobs for transfer to be delayed until as close as possible to the moment of transfer. The operation of the protocol is described for each phase and synchronisation of the parallel activities in the virtual rings is discussed. The schedule length performance of the distributed algorithm is examined in a series of closed-system tests.