Is a real time kernel really needed?

Have set up a LinuxCNC workstation on Debian Jessie and can switch between the 3.16.0 kernel and the 3.2 RT kernel from Wheezy.

Have seen some problems with the RT kernel so have been researching real time kernels and applying RT patches. In researching various kernels and real time patches, I learned that the "vanilla" kernels are capable of millisecond latencies. This raises the question in the subject line. Is it really necessary to use a real time kernel with most LinuxCNC applications?

In my case, I am interested in building a cnc router for woodworking and also a cnc lathe. It would seem that my feed rates would be low enough thst millisecond range latencies would be OK.

Am I overlooking something?

I am not an expert but:

vanilla kernels do not _guarantee_ millisecond latencies.
You don't mention what kind of hardware you are using either - software stepping is much less tolerant.
Read here for an idea why:
wiki.linuxcnc.org/cgi-bin/wiki.pl?Tweaki...setup_and_or_dirhold
it also isolates problems of GUI controls from machine movement. There are reports of the computer not responding to keyboard or mouse movement but the CNC continued to finish the machining with no problems.

But the practical experience may show that your machining needs are fault tolerant and/or your hardware is good enough.
but if you have work glitched or crash your machine because the controls didn't react soon enough.....

Chris M

Makes sense. There's a big difference between "guarantees" and "capable of".

I'll keep studying. I haven't been able to work so deeply in real-time systems since the 1970's. This is fun!