Improving GPOS Real-Time Responsiveness Using vCPU Migration in an Embedded Multicore Virtualization Platform

In this paper, a vCPU (virtual CPU) migration mechanism in order to improve real-time responsiveness in a GPOS (General Purpose Operating System) is presented in the embedded multicore virtualization platform and can also be applied to CPS environment. Virtualization technique is recently emerging as a useful solution for the embedded system, because it can provide real-time handling ability through a RTOS (Real Time Operating System), and use a GPOS to deal with other tasks like windowing or entertaining services. However, tasks in GPOS now also need some degree of real-time services from the system. For example, the audio or video tasks. Unfortunately, in a traditional virtualization platform, a virtualization layer always gives RTOS vCPU higher priority and preempts the execution of GPOS. The reason for this phenomenon is that the underlying virtualization layer has no additional scheduling information provided. Therefore, a kernel module in the GPOS is added in our virtualization system to export and boost a GPOS vCPU contexts which needs higher priority against RTOS vCPU. At the same time, in order not to sacrifice the performance of the victim RTOS vCPU, a vCPU migration mechanism is added to our virtualization system, and migrates the RTOS vCPU to a low-loading CPU when this vCPU is preempted. Performance improvement of GPOS's real-time responsiveness is also given while a detailed analysis of the overhead of the RTOS vCPU is performed as well. The result showed that the migration overhead of a RTOS vCPU is under an acceptable level. This also means that one can use our approach to improve the GPOS's performance, while keeping RTOS's real-time responsiveness at the same time.