too long hm2_7i97.0.read.tmax or something else?

00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (7) I219-V (rev 10)
DeviceName: Onboard - Ethernet
Subsystem: Lenovo Ethernet Connection (7) I219-V
Flags: bus master, fast devsel, latency 0, IRQ 120
Memory at b1000000 (32-bit, non-prefetchable) [size=128K]
Capabilities: <access denied>
Kernel driver in use: e1000e
Kernel modules: e1000e

eee was already off, not sure about gro, lro or tso but I will try with them disabled also.

Looking at your first post, its not network related. Note those previous settings do not persist. Running out of ideas. As PCW mentioned ensure the NIC interrupt is pinned to isolated core 5

You mentioned graphics so you probably have an Intel i915 GPU which hangs on my PC. Add these to grub to lock it downi915.enable_dc=0 i915.enable_fbc=0 i915.enable_psr=0 

After adding downi915.enable_dc=0 i915.enable_fbc=0 i915.enable_psr=0 to grub, and creating another thread for all non-motion related stuff I got servo-thread time down to ~400000 and tmax 1351609 (did not increase after startup). Not realtime delay errors so far.

Also tried again with [HMOT](CARD0).read-request in the end of servo-thread just for fun. It definitely shortens read.time, servo-thread time drops to around 50000, but something breaks and i get following error spikes in every 75ms (pyvcp refresh rate). I would be interested to know why, any speculations welcome.

But most importantly it seems to be working now. Thanks for help rodw and PCW.

Just in case anybody has to deal with similar problems:
I had to investigate a bit further since the spiking came back, but I think it might be working now. The spiking indeed was graphics related, this thread is slightly misplaced now but anyway.

Software rendering seems to work the best with this hardware:
LIBGL_ALWAYS_SOFTWARE=1 QT_OPENGL=software MESA_LOADER_DRIVER_OVERRIDE=llvmpipe \

So OpenGL Mesa this time, not the usual Mesa:)
I don't know if it is a good practice to use software graphics but I'm open to suggestions.