A hierarchical processor scheduling policy for distributed-memory multicomputer systems

Processor scheduling policies for distributed memory systems can be divided into space sharing or time sharing policies. In space sharing, the set of processors in the system is partitioned and each partition is assigned for the exclusive use of a job. In time sharing policies, on the other hand, none of the processors is given exclusively to jobs; instead, several jobs share the processors (for example, in a round robin fashion). There are advantages and disadvantages associated with each type of policy. Typically, space sharing policies are good at low to moderate system loads and when job parallelism does not vary much. However, at high system loads and widely varying job parallelism, time sharing policies provide a better performance. We propose a new policy that is based on a hierarchical organization that incorporates the merits of these two types of policies. The new policy is a hybrid policy that uses both space sharing as well as time sharing to achieve better performance. We demonstrate that, at most system loads of interest, the proposed policy outperforms both space sharing and time sharing policies by a wide margin.