Xen on ARM Interrupt Latency
Xen on ARM is becoming more and more widespread in embedded environments. In these contexts, Xen is employed as a single solution to partition the system into multiple domains, fully isolated from each other, and with different levels of trust.
Every embedded scenario is different, but many require real-time guarantees. It comes down to interrupt latency: the hypervisor has to be able to deliver interrupts to virtual machines within a very small timeframe. The maximum tolerable lag changes on a case by case basis, but it should be in the realm of nanoseconds and microseconds, not milliseconds.
Xen on ARM meets these requirements in a few different ways. Firstly, Xen comes with a flexible scheduler architecture. Xen includes a set of virtual machine schedulers, including RTDS, a soft real-time scheduler, and ARINC653, a hard real-time scheduler. Users can pick the ones that perform best for their use-cases. However, if they really care about latency, the best option is to have no schedulers at all and use a static assignment for virtual cpus to physical cpus instead. There are no automatic ways to do that today, but it is quite easy to achieve with the vcpu-pin command:
Read the entire article here, Xen on ARM interrupt latency
via the fine folks at Xen.org.