Hi Dr. Schöpfer,
please have a look to the test rack at the OASDL homepage and you will see that the same release of PREEMPT_RT is performing very different on different motherboards.
IMHO ... the most important issue is the SMI interrupt and the triggered execution of the low level firmware of the motherboard. Also a transaction on the PCI bus using DMA transfers can increase the response time on a single core ...
Best Regards Armin http://www.steinhoff-automation.com Dr.-Ing. Matthias Schöpfer schrieb:
Hi Thomas Winding, thanks for your answer! We are running kernel 3.12.31-rt45, since the newer kernel versions do not seem to run as reliable regarding real time at least on our hardware. ethercat is from the mecurical repository and we use the e1000e driver. Most of our problems we might have solved, since we had an issue with our cycle time / calculations where sometimes, our cycle lasted 600-800 microseconds, which seems to be way to long. We are now down to < 220 microseconds. In rare cases, when we start the software, we still constantly running in the mentioned issues. When we stop and restart, everything is fine. I wonder, if we sometimes hit a misfortuned timing. As of lately, I was not able to reproduce it. Regarding your suspicion: I wonder, if it is better to sync the transmits to the 1 ms cycle instead of the receives?! Regards, Matthias Schöpfer On 02/01/2016 09:07 AM, Thomas Winding wrote:Hi Matthias Schöpfer I have seen the same problem. I am also running at 1 ms and using clock_nanosleep. I suspect that the problem arise when you send a new telegram before you have received the previously send telegram. Which version of the ethercat are you using? Which version of kernel are you using? Best regard, Thomas Winding -----Original Message----- From: etherlab-dev [mailto:etherlab-dev-boun...@etherlab.org] On Behalf Of Dr.-Ing. Matthias Schöpfer Sent: 26. januar 2016 14:22 To: etherlab-dev@etherlab.org Subject: [etherlab-dev] Possible Realtime Issues with Ethercat Master and RT Preempt Kernel Hi! We started using etherlab/ethercat and are quite impressed. Nice work! We are running Linux with a RT_PREEMPT Kernel and e1000e ethercat driver. We have to run at a cycle time of 1ms and we have jitter from clock_nanosleep of about 15 microsecs max. Nevertheless, we suffer from time to time from these: EtherCAT WARNING 0: 2 datagrams UNMATCHED! EtherCAT 0: Domain 0: Working counter changed to 9/9. EtherCAT 0: Domain 0: Working counter changed to 0/9. Especially, when we apply load to the system. From previous projects, I experienced these effects when IRQ/Kernel Thread was not set to appropriate RT Level. My Question: has anybody experienced similar problems, and would it be worth to investigate it. And if I decide to patch the kernel module, where is a good starting point. Thanks and regards, Matthias Schöpfer -- Dr. Matthias Schöpfer mz robolab GmbH Marie-Curie-Str. 1 53359 Rheinbach Office: +49 2226 83600 00 Fax: +49 2226 83600 11 Email: schoep...@robolab.de mz robolab GmbH Vertretungsberechtigte GeschÀftsfÃŒhrer: Dr. RÃŒdiger MaaÃ, Ralf Schulte Registergericht Amtsgericht Bonn Registernummer HRB 10595 --- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorised copying, disclosure or distribution of the material in this e-mail is strictly forbidden. Diese E-Mail enthÀlt vertrauliche und/oder rechtlich geschÃŒtzte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtÃŒmlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet. --- P please consider the environment before printing this e-mail _______________________________________________ etherlab-dev mailing list etherlab-dev@etherlab.org http://lists.etherlab.org/mailman/listinfo/etherlab-dev
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