Dates and Events: |
OSADL Articles:
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
2017-09-12 12:00
OSADL project to create Open Source license checklists
Facilitate Open Source software delivery
2016-09-17 12:00
Preemption latency of real-time Linux systems
How to measure it – and how to fix it, if it's too high? |
The basis for Real-Time Ethernet protocols in Linux
Thomas Gleixner and Sebastian Siewior, Linutronix GmbH, Germany
Even if the latest PREEMPT_RT patched Linux kernel is used, the network stack can inflict unbound latencies on real-time Ethernet protocols due to:
- Socket buffer allocations
- Traffic congestion with non real-time traffic
In a proof-of-concept implementation, the following mechanisms are used
to overcome the above limitations:
- Generic preallocated socket buffer pools
- Protocol-specific traffic policing and traffic shaping
This approach is minimally invasive to the network stack and has zero impact when the real-time protocol related functions are not enabled:
- Network card drivers require no or minimal changes to support preallocated buffer pools
- Traffic control is modular and only loaded and enabled when required
- No restriction on network tools and network functionality
The paper does not cover the complex user space part of real-time Ethernet protocols.
