Task Grain Scheduling for Hypervisor-Based Embedded System

The emergence of functional embedded systems such as cell-phones and digital appliances brought up a new issue, building a system supporting both real-time and rich services. One of the solutions is leveraging a hypervisor to integrate an RTOS and a commodity OS into a single device. However, this approach induces the limitation of application deployment; all the high priority tasks should reside in the RTOS. In this paper, we propose a task grain scheduling for a real-time hypervisor, which enables a flexible application deployment between an RTOS and a commodity OS. We constructed a prototype system with an existing hypervisor, an RTOS, and a commodity OS. We measured some basic overheads, and fixed some tasks which were missing their deadlines using the task grain scheduling to meet their deadlines. The overheads were small and the task grain scheduling achieved a flexible real-time scheduling for the hypervisor based system.