Thermal-Aware Servers for Real-Time Tasks on Multi-Core GPU-Integrated Embedded Systems

The recent trend in real-time applications raises the demand for powerful embedded systems with GPU-CPU integrated systems-on-chips (SoCs). This increased performance, however, comes at the cost of power consumption and resulting heat dissipation. Heat conduction interferes the execution time of tasks running on adjacent CPU and GPU cores. The violation of thermal constraints causes timing unpredictability to real-time tasks due transient performance degradation or permanent system failure. In this paper, we propose a thermal-aware server framework to safely upper bound the maximum temperature of GPU-CPU integrated systems running real-time sporadic tasks. Our framework supports variants of real-time server policies for CPU and GPU cores to satisfy both thermal and timing requirements. In addition, the framework incorporates two mechanisms, miscellaneous-operation-time reservation and pre-ordered scheduling of GPU requests, which significantly reduce task response time. We present analysis to design thermal-server budget and to check the schedulability of CPU-only and GPU-using sporadic tasks. The thermal properties of our framework have been evaluated on a commercial embedded platform. Experimental results with randomly-generated tasksets demonstrate the performance characteristics of our framework with different configurations.

I. Introduction

High temperature in embedded systems with modern systems-on-chips (SoCs) causes several major issues. An increase in temperature has a considerable impact in the growth of leakage current which leads to rise in static power consumption. An increase in power consumption levels up the device temperature, thereby resulting in again an increase in power consumption. This detrimental loop causes not only rapid battery drain but also "thermal runaway" [3]. Furthermore, studies show that operating in high temperature reduces the system reliability substantially [42]. For instance, 10°C to 15°C increase in temperature doubles the probability of failure of the underlying electronic devices [44]. Thermal violation not only reduces the reliability in real-time implantable medical devices, but also causes physical harm [6]. Therefore, bounding the maximum temperature is an important issue, especially when real-time requirements have to be satisfied.