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Later versions of Debian (we use debian 12 bookworm) requires careful optimisation on 2 core machines. I would suggest a 4 core Celeron, 4gb RAM, any sized SSD

Thanks Rod,

I gave this a try because I was excited to read that "This release includes realtime support (PREEMPT_RT), a feature that has been in the works for 20 years." So is there a bug in the PREEMPT_RT support in the 6.12 kernel, or is it simply not implemented the way LinuxCNC has come to expect? Obviously LinuxCNC needs to support a working standard.

Yes. you could try sudo apt install linux-image-rt-arm64

Yes the kernel needs to be specifically built to support preempt_rt even in kernel 6.12
It seems that on the Pi a default 6.12 RT kernel build is not recognised by linuxcnc unless the kernel has additional settings that are provided in the patch. This may end up being fixed by the kernel developers in later versions

This may not be relevant to you but building a custom image that includes Linuxcnc is not trivial and requires building a kernel from source so it needs to be a RT kernel.


 

I'm trying to do this with an Rpi 4 and I'm seeing the same thing. I can find the PID of latency-histogr. Then run chrt -p PID which reports that current scheduling policy as SCHED_OTHER. Then run chrt -f -p PID which does change the scheduling policy to SCHED_FIFO.

But all I did (hoped was necessary) was to update the kernel. sudo rpi-update next, thne reboot. Must one actually build the kernel with a patch? That seems odd if the kernel offers full RT support.

Oh, it's part of the Kernel files isn't it. Ugh.

Roy,

I've updated the kernel to 6.12.8 on an Rpi 4, and I'm seeing pretty much the same behavior. However, I'm not finding the file you patched anywhere on the system? sudo find / -print | grep ksysfs finds nothing.

Thanks,

Gene