UI unresponsive on larger files

I am facing an issue that with larger files (>3 MB) the UI is completely locking up for minutes. Meaning, (almost) all buttons are unresponsive for two minutes after loading the file, then again after for example pressing the "clear path" button. Also during the job most buttons take two minutes to react, so it prevents me from pausing a job, for example. A tool change dialog also takes minutes to appear.

CPU and Memory usage are low in the process monitor during this time.

Interestingly one button from a custom tab that I added for switching my vacuum pump always works perfectly during the frozen UI.
However, removing all custom tabs also doesn't help.

I found a forum post where somebody recommended upgrading the Linux kernel to version 5, which I did, but I perceive no change.

$ uname -a
Linux cnc 5.10.0-0.deb10.23-rt-amd64 #1 SMP PREEMPT_RT Debian 5.10.179-1~deb10u1 (2023-05-26) x86_64 GNU/Linux

$ lsb_release -a
No LSB modules are available.
Distributor ID:    Debian
Description:    Debian GNU/Linux 10 (buster)
Release:    10
Codename:    buster

$ cat /proc/meminfo | grep MemTotal
MemTotal:        7956232 kB

$ cat /proc/cpuinfo | head -5
processor    : 0
vendor_id    : GenuineIntel
cpu family    : 6
model        : 122
model name    : Intel(R) Celeron(R) J4125 CPU @ 2.00GHz

Any other idea what could be a reason?[/quote]

It looks like it is CPU related after all, but I found no solution. Here is a screenshot of CPU utilization:

 

The time where utilization is 50% is where the UI is frozen. Since the CPU has 4 cores and the base load is 25-30% when the UI is not frozen, I'd say this looks like one core being fully utilized - probably the core that is also supposed to update the UI. Still no idea what causes this and how to prevent it.

After more experimentation I can say that the problem is even visible in tiny gcode files, to some extent: I have a small gcode file (50KByte) that loads fast, but then

- if I drag it around in the preview window it works perfectly fast.
- As soon as I let go of the mouse button, it freezes for a second or so.
- After that second, I see the gcode line highlighted in MDI and in the preview plot, and the UI is responsive again.

So I think it may be related to code that tries to do this highlighting.
I can confirm that the freezes do not happen when adding​​​​​​ (AXIS,hide) and (AXIS,show) to the gcode, but that is throwing out the complete preview, not just the highlighting.

Can I disable the highlighting feature somehow?
 

So, I fixed it:

vi /usr/lib/python2.7/dist-packages/rs274/glcanon.py

In the select() method, comment this out:

if self.get_show_rapids():
    glCallList(self.dlist('select_rapids', gen=self.make_selection_list))
glCallList(self.dlist('select_norapids', gen=self.make_selection_list))

github.com/LinuxCNC/linuxcnc/issues/2539