Which kernel version is best for real time?

Perhaps try this:

Save your config files somewhere very safe.

Open your PC and remove all unnecessary hardware (except the GPU).

Reinstall LinuxCNC from the official ISO. (The latest version, or perhaps some earlier version).

Set CPU governor to performance.

Run latency test.

See if latency is improved.

Changing the scaling govenor to performance reduced my latency a noticable amount.

echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

unknown wrote:

Warning: Spoiler!

Sorry I meant 2.9.4 Try not to get bogged down with latency. Test the machine running code, if it works don't worry too much about it. I took the gcode file that loads when you first start Axis, made it into a loop, loops thru the gcode about a hundred times,if I don't get any errors I'm confident it will be fine. I really don't think there will be much difference between a modular or monolithic kernel. You can gain a bit by fiddling with mount options, looking for any background services that aren't needed, I generally disable sound and I'll disable wifi if it's not required. You'll find this forum a lot different to cnczone, for one no one on here gets caught playing my rapids are this fast, also you won't here anyone saying that you need to be a programmer to use Linuxcnc. It works and works well. Almost any issues you have will have been discussed many many ten times over. 99.99% of the reason Linuxcnc won't start is a typo somewhere in the hal & ini files. Sometimes I think that running the latest kernel on older CPUs isn't the best course of action. Far better to have some extra latency and a stable system. Look you can spend a lot of time building different kernels and trying all the tricks in the book to lower latency, but as long as latency is, as a rule thumb, below 100,000 ns for an external step/direction generator you're good to go. Then again network latency can be a PITA to sort sometimes.