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2024-10-03 - 16:03

Dates and Events:

OSADL Articles:

2024-10-02 12:00

Linux is now an RTOS!

PREEMPT_RT is mainline - What's next?


2023-11-12 12:00

Open Source License Obligations Checklists even better now

Import the checklists to other tools, create context diffs and merged lists


2023-03-01 12:00

Embedded Linux distributions

Results of the online "wish list"


2022-01-13 12:00

Phase #3 of OSADL project on OPC UA PubSub over TSN successfully completed

Another important milestone on the way to interoperable Open Source real-time Ethernet has been reached


2021-02-09 12:00

Open Source OPC UA PubSub over TSN project phase #3 launched

Letter of Intent with call for participation is now available



Real Time Linux Workshops

1999 - 2000 - 2001 - 2002 - 2003 - 2004 - 2005 - 2006 - 2007 - 2008 - 2009 - 2010 - 2011 - 2012 - 2013 - 2014 - 2015

13th Real-Time Linux Workshop from October 20 to 22 at the Faculty of Electrical Engineering, Czech Technical University in Prague

Announcement - Hotels - Directions - Agenda - Paper Abstracts - Presentations - Registration - Abstract Submission - Sponsoring - Gallery

openPOWERLINK in Linux Userspace: Implementation and Performance Evaluation of the Real-Time Ethernet Protocol Stack in Linux Userspace

Wolfgang Wallner, Wolfgang Seiss, Josef Baumgartner, Bernecker + Rainer, Austria

The RT-Preempt patch for Linux turns the Linux operating system into a real-time operating system and therefore is an ideal platform to implement a real-time Ethernet protocol stack like openPOWERLINK. The initial implementation of the openPOWERLINK stack on X86 Linux was developed as a kernel module. The solution completely bypasses the Linux network stack and achieves maximum performance through the usage of its own network interface drivers. However, this limits the protocol stack to the few openPOWERLINK network interface drivers currently available and also makes the protocol very dependent on the used kernel version. To circumvent these drawbacks, the whole protocol stack was implemented as Linux userspace library. As most of the necessary real-time features are also available in userspace and many applications do not need the performance level of the kernelspace implementation, this solution is adequate for a lot of applications.

This paper describes the porting of the openPOWERLINK stack to userspace and examines the performance of the userspace implementation. Therefore, the influence of the userspace implementation on the network jitter and on the generated system load is analyzed and compared with the kernelspace implementation. Due to the long term goal to integrate the lower level layers of the openPOWERLINK stack into the mainline Linux kernel, in this paper it is furthermore discussed how the protocol stack could be segmented into a kernel part that would be integrated into the Linux kernel and a user part that is provided as a userspace library.