KaeilOS : Real Time

Linux kernel has not been designed thinking to a Real Time system and therefore if you are looking for true determinist performances is necessary to use some Real Time extension like RTAI and Xenomai, or in alternative RT Preemption patch.

Xenomai

The realtime framework for linux.

UVM support is a unique Xenomai feature, which allows running a nearly complete realtime system embodied into a single multithreaded Linux process in userspace, hence the name, standing for "Userspace Virtual Machine".
Running a realtime application inside a UVM offers a straighforward approach for porting from other RTOS environments to Xenomai. For this reason, all emulators of traditional RTOS available with Xenomai (e.g. VxWorks, pSOS+, VRTX, and uITRON) can be hosted by UVMs, although they were initially intended to run as kernel modules.

 

RTAI

The RealTime Application Interface for Linux from DIAPM (Politecnico di Milano - Dipartimento di Ingegneria Aerospaziale)

RTAI offers the same services of the Linux kernel core, adding the features of an industrial real time operating system. It consists basically of an interrupt dispatcher: RTAI mainly traps the peripherals interrupts and if necessary re-routes them to Linux. It is not an intrusive modification of the kernel; it uses the concept of HAL (hardware abstraction layer) to get information from Linux and to trap some fundamental functions. This HAL provides few dependencies to Linux Kernel. This leads to a simple adaptation in the Linux kernel, an easy RTAI port from version to version of Linux and an easier use of other operating systems instead of RTAI. RTAI considers Linux as a background task running when no real time activity occurs.

 

Low Latency Patch & RT Preemption Patch

Ingo Molnar's RT-Preemption patch aims to bring hard-realtime scheduling latencies (50-60 microseconds worst case execution time) to the Linux kernel.