Yocto is the most famous build system for embedded Linux. Today most of BSPs are provided as Yocto "recipes" and/or metadata.

They are several extensions providing RT capabilities to the Linux kernel. Number one is PREEMPTRT, maintained by Thomas Gleixner and supported by the Linux foundation since 2015. Second one is Xenomai mainly based on a co-kernel architecture (such as RTLinux). It was created by Philippe Gerum, a french RT expert and is maintained by a small group of contributors. Current version is 3.0.5 and can be used in dual kernel mode (Cobalt) or on top of PREEMPTRT in a single kernel approach (Mercury).

Using RT extension with Yocto is not that easy because linux-yocto-rt kernel is not usable on main embedded target such as ARM (as it works on QEMU target only). Using Xenomai is much more complicated as it needs several steps (patching the kernel, installing user-space libraries, building an extended SDK).

During the conference we will decribe how to build a Yocto Linux image using PREEMPT_RT for famous boards such as Pi 3 or BeagleBone Black.

Some Xenomai support is provided by meta-eldk from DENX but it supports only Xenomai 2.6. We will describe meta-xenomai as we maintain it for our customers (available on GitHub). That new meta-xenomai layer is based on Xenomai 3.x and very recent kernel.

Then we will explain how to build a simple Xenomai application based on a periodic task. Finally we will compare performances of both extension (PREEMPT_RT and Xenomai) on same hardware.