Dear real time community, we are long-time users of PREEMP_RT on more platforms and work on CAN/CAN FD, motion control support for Linux, and other RTOSes. We contributed by CAN latency testing for decades, and we run our latest solution for CAN latency testing on Linux mainline and PREEMP_RT kernel continuously from March 2023 https://canbus.pages.fel.cvut.cz/#can-bus-channels-mutual-latency-testing https://canbus.pages.fel.cvut.cz/can-latester/ We use the attached configuration file. Please check if you find some problematic choices. The cyclic test worked well, and we have even delivered two systems to OSADL QA real-time farm https://www.osadl.org/?id=4109 The maximal latency is under 200 usec, we have run even pysimCoder https://github.com/robertobucher/pysimCoder and Matlab/Simulink generated code at 4 kHz for PMSM control etc. https://github.com/aa4cc/ert_linux All works well. However, the CAN/CAN FD communication latency measured on the CTU CAN FD IP core is far from optimal. Some runs under load with 10 msec latency. Our own CAN FD stack for RTEMS keeps with no exception under 60 usec on the same hardware. I understand that the Linux socket layer and networking stack are complex, and many optimizations are ahead. We will be happy to contribute where we can and find time and even some resources to engage more students etc... But I would like to be sure that the bad results are not caused by our mistakes in configuration. I will be happy to meet you and discuss Linux and other control and real-time areas at FOSDEM 2025. I have had an interest in presenting there our students' projects, open-source motion control system https://gitlab.fel.cvut.cz/otrees/motion/samocon and online aid/website for training, exercises and education of computer architectures build around our QtRvSim simulator https://comparch.edu.cvut.cz/online-tools/webeval/ But these talks has not been accepted. I even offered to talk about PREEMP_RT and our control and CAN projects because I have prepared one for our local community in Czech. That talk has been accepted, and it seems that no other developer more familiar with Linux RT has submitted the talk, so I will try to cover even some remembrance of PREEMPT_RT history. But I would be happy to receive feedback and suggestions for corrections. Original talk in Czech https://talks.openalt.cz/openalt-2024/talk/3XTMDF/ Slides in English which I want to update/correct for FOSDEM https://talks.openalt.cz/media/openalt-2024/submissions/3XTMDF/resources/openalt24_linux_for_rt-reduced_FbZPuS0.pdf FOSDEM 2025 talk abstract https://fosdem.org/2025/schedule/event/fosdem-2025-5411-linux-kernel-mainline-real-time-history-support-and-experience-based-on-robotic-and-automotive-projects/ Best wishes, Pavel Pavel Pisa phone: +420 603531357 e-mail: pisa@xxxxxxxxxxxxxxxx Department of Control Engineering FEE CVUT Karlovo namesti 13, 121 35, Prague 2 university: http://control.fel.cvut.cz/ personal: http://cmp.felk.cvut.cz/~pisa company: https://pikron.com/ PiKRON s.r.o. Kankovskeho 1235, 182 00 Praha 8, Czech Republic projects: https://www.openhub.net/accounts/ppisa social: https://social.kernel.org/ppisa CAN related:http://canbus.pages.fel.cvut.cz/ RISC-V education: https://comparch.edu.cvut.cz/ Open Technologies Research Education and Exchange Services https://gitlab.fel.cvut.cz/otrees/org/-/wikis/home
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