A study on real-time responsiveness on virtualization based multi-OS embedded systems

Despite the strong requirement of supporting deterministic real-time scheduling on virtualization based multi-OS embedded systems, which enables co-location of a real-time operating system and a generalpurpose operating system on a single device, there are few investigations in the real-world hardware. In this paper we introduce our virtualization layer called SPUMONE, which runs on single-core and multi-core SH-4A processors. SPUMONE achieves the low overhead, and requires a small amount of engineering efforts to modify guest OS kernels for executing on SPUMONE. SPUMONE now can execute the TOPPERS real-time OS and Linux as a general-purpose OS concurrently on a single embedded platform. In addition we propose two techniques to mitigate the interference of Linux to the real-time responsiveness of RTOS. The first technique leverages the interrupt priority level mechanism supported by the SH-4A processor. The second is the proactive migration of a virtual core among physical cores to prevent the Linux kernel activity from blocking the interrupts assigned to RTOS. The evaluation shows that our techniques can decrease the interrupt latency of RTOS entailed by Linux. In addition, sharing a physical core between RTOS and Linux will increase total processor utilization.