1. Experiments
● Evaluate the impact of virtualization on the RTOS's overheads and latencies
● Measure a set of fine-grained RTOS's overheads and latencies
● Compare the measurements from a virtualized RTOS and a native RTOS
Test Platform
● Host OS: real-time Linux, configured with PREEMPT_RT
● Virtual Machine Monitor: KVM/Qemu
● Guest RTOS: Litmus^RT installed in a VM
● Native configuration: Litmus^RT installed on a bare-metal hardware
Reasons for performance degradation
● Emulation of I/O interrupt by the virtual machine monitor
● Scheduling of virtual machines processes by the host OS
Discussion
● worst-case of some latencies may be far from average-case
● Difficult to draw conclusions only from overheads comparison
● Develop new real-time scheduling theory that take into
account the overhead introduced by the virtualization
Hardware
kvm driver
Virtual Machine
kvm
Applications
Guest RTOS
Qemu
Host
Applications
Linux
Unprivileged
mode
Privileged
mode
dual-core Intel 1.86GHz hardware
Evaluation of the RTOS's Overheads and Latencies on a Hosted Virtual Machine System
Virtualized RTOSNative RTOS
Mehdi Aïchouch
Overheads & Latencies