Least-space-time-first scheduling algorithm: A policy for complex real-time tasks in multiple processor systems

Abstract

Significant prior work exists on scheduling for the ‘simple-tasks-single-processor’, ‘simple-tasks-multiple-processor’, and ‘complex-tasks-single-processor’, but few researchers have yet considered the ‘complex-tasks-multiple-processor’ model. We propose a new algorithm, Least Space-Time First (LSTF), to deal with the general ‘complex-task-multiple-processor’ model. We demonstrate that LSTF outperforms the Highest-Level-First, Earliest-Deadline-First and Least-Laxity-First scheduling disciplines in the sense of minimizing maximum tardiness of a set of tasks. LSTF can gracefully incorporate some realistic overhead assumptions, including context switch and communication. The Unit Precedence Graph and Soft-Precedence Edges significantly facilitate implementation of LSTF.