Raspberry Pi 4

Hakan / wicki can you add some details here:
github.com/guysoft/RealtimePi/issues/17#issuecomment-511322405
guysoft makes the RealtimePi images, and TiejunChina does the "official" rpi-4.19-y-rt style builds.
But it seems that neither of them own a Pi4 for testing with.

I tested today again with a new sd card. Well it was better but didn't really solve anything.

If I run latency-histogram for under 1 minute I get similar looking graph like wicki's.
The previous graph I posted ran for 1.5 hour with me surfing and 7? glxgears.

I can't see there is a real difference otherwise. I used the 4.19.57 kernel with the RT-patches for 4.19.50, but it shouldn't matter, the RT-patches don't change that much and the patching was clean with just a few line offsets. wicki used 4.19.50 for kernel and rt-patches. There is a difference of course.

wicki what does the latency-histogram look after, say, 10 minutes?

And does it work running linuxcnc, that is of ocurse the interesting question.
wicki, if you are busy testing I think I'll wait for your results.

Have you tried futzing with isolcpus?
EDIT: I had to set isolcpus=1,2,3 to get decent latency on my RPI3/LinuxCNC test machine:

No.

Well now I have. And it made all the difference in the world.
The following is with wlan0 disabled. Leaving wlan0 up and surfing at the same time
has a huge impact on the latency numbers.Surfing brings the max latency numbers
up a factor 5, around +- 100 us.




I can try some more tomorrow, it's getting late here.

I have tried some, but not yet been able to get a step going. I use the 7i76E mesa card via the ethernet port.
It is possible to get it going to the point where gmoccapy is displayed and reacts to Machine On/Off.
The 7i76E displays all the inputs and outputs as it scrolls by during startup.
But when I try to jog, there is a core dump by rtapi_app. No steps are taken.

I have noticed that "iptables -N hm2-eth-rules-output2 fails with "iptables: Operation not supported"
Obviously iptables is gone, say hello to nftables. Or That helps for those messages.
Still, when I jog the tiniest distance I get and then there is no reaction.

I guess you are building from source? Can you try this:

github.com/LinuxCNC/linuxcnc/blob/master/docs/rtfaults.txt

This will tell us where, and in which file, the core dump is happening.