Towards real-time scheduling of virtual machines without kernel modifications

Virtualization is a well used technique in the area of internet server systems for managing several (legacy) applications on a single physical machine. These applications do not have strict time deadlines, which also reflects how these applications are scheduled. Using virtualization in an embedded real-time systems context is of course attractive, since we want to pack as much software as possible on a, as small as possible, hardware platform. The problem is that this kind of software does not easily cope well together, in the aspect of time related properties. Hence, we need a new mechanism, i.e., a scheduler, that can satisfy the timing requirements of each application. However, scheduler implementations typically require modifications to middleware or kernel and this is not acceptable in the area embedded systems, due to stability and reliability reasons. Hence, in this paper, we propose a framework for scheduling (soft real-time) applications residing in separate operating systems (virtual machines) using hierarchical fixed-priority preemptive scheduling, without the requirement of kernel modifications.