Mesa hm2/hm2_7i96s.0: error finishing read

increasing the servo period to 1.5ms instantly made my worse case blip 2.4M, not exactly sure what that means.

it probably means that packets were being dropped (timed-out)
at a 1 ms servo thread rate (default timeout is 80% of servo period)

GRUB_CMDLINE_LINUX_DEFAULT="quiet lapic=notscdeadline hpet=disable i915.i915_enable_rc6=0 i915.powersave=0 intel_idle.max_cstate=1 processor.max_cstate=1 isolcpus=1 idle=poll"

That little lot significantly improves things it makes much more stable, it reduces the frequency and magnitude of the big delay spikes.

You might also try running Intels powertop utility and setting all power saving options to "bad"

So extending the servo period does not seem to overcome the issues as the read.tmas also extends when the timing spikes occur, i left it on soak test overnight and sure enough i got an "error finishing read! iter=" my read hm2_7i95.0.read.tmax hit a record 3376032 and servo .tmax hit 3597792 both with servo period set to SERVO_PERIOD = 2000000 I will try the exact hw with my older 2.8 build and also some different hw with this setup and post the results. Is it possible to make the error finishing read non fatal?

The issue follows the OS / Kernel or LinuxCNC version, not the hardware (hardware has small effect). Will post the stats later.