Supporting Soft Real-Time Sporadic Task Systems on Heterogeneous Multiprocessors with No Utilization Loss

TL;DR

This paper demonstrates that soft real-time sporadic task systems can be effectively scheduled on heterogeneous multiprocessors without utilization loss, ensuring bounded response times with a novel GEDF-H algorithm.

Contribution

It introduces GEDF-H, the first scheduling algorithm that guarantees bounded response times for soft real-time tasks on heterogeneous multiprocessors without utilization loss.

Findings

Response time bounds are often smaller than three task periods.

GEDF-H performs well under both preemptive and non-preemptive scheduling.

This approach is the first to support soft real-time systems on heterogeneous architectures without utilization loss.

Abstract

Heterogeneous multicore architectures are becoming increasingly popular due to their potential of achieving high performance and energy efficiency compared to the homogeneous multicore architectures. In such systems, the real-time scheduling problem becomes more challenging in that processors have different speeds. A job executing on a processor with speed $x$ for $t$ time units completes $(x \cdot t)$ units of execution. Prior research on heterogeneous multiprocessor real-time scheduling has focused on hard real-time systems, where, significant processing capacity may have to be sacrificed in the worst-case to ensure that all deadlines are met. As meeting hard deadlines is overkill for many soft real-time systems in practice, this paper shows that on soft real-time heterogeneous multiprocessors, bounded response times can be ensured for globally-scheduled sporadic task systems with no utilization loss. A GEDF-based scheduling algorithm, namely GEDF-H, is presented and response time bounds are established under both preemptive and non-preemptive GEDF-H scheduling. Extensive experiments show that the magnitude of the derived response time bound is reasonable, often smaller than three task periods. To the best of our knowledge, this paper is the first to show that soft real-time sporadic task systems can be supported on heterogeneous multiprocessors without utilization loss, and with reasonable predicted response time.