Flattening hierarchical scheduling

Abstract

Recently, the application of virtual-machine technology to integrate real-time systems into a single host has received significant attention and caused controversy. Drawing two examples from mixed-criticality systems, we demonstrate that current virtualization technology, which handles guest scheduling as a black box, is incompatible with this modern scheduling discipline. However, there is a simple solution by exporting sufficient information for the host scheduler to overcome this problem. We describe the problem, the modification required on the guest and show on the example of two practical real-time operating systems how flattening the hierarchical scheduling problem resolves the issue. We conclude by showing the limitations of our technique at the current state of our research.