Micro-preemption synthesis: an enabling mechanism for multi-task VLSI systems

Task preemption is a critical enabling mechanism in multi-task VLSI systems. On preemption, data in the register files must be preserved in order for the task to be resumed. This entails extra memory to preserve the context and additional clock cycles to save and restore the context. In this paper, we present techniques and algorithms to incorporate micro-preemption constraints during multi-task VLSI system synthesis. Specifically, we have developed: (i) Algorithms to insert and refine preemption points in scheduled task graphs subject to preemption latency constraints. (ii) Techniques to minimize the context switch overhead by considering the dedicated registers required to save the state of a task on preemption and the shared registers required to save the remaining values in the tasks. (iii) A controller based scheme to preclude preemption related performance degradation. The effectiveness of all approaches, algorithms, and software implementations is demonstrated on real examples.