I am having a mysterious issue with my i3 KDE Desktop running Kubuntu 20.04, with the Linux 5.7.9 kernel.

- The only reason I run the near-latest kernel, was to try and resolve this issue. Normally I run a kernel a few versions behind.
- I am not sure when exactly this started happening, but it is sometime after I updated to Kubuntu 20.04.

- The issue I am having is random and frequent UI freezing.
- The problem seems to be independent of the program I am using.
- The UI becomes unresponsive, taking several seconds to react to input. E.g. clicking or selecting text.
- Only the active program seems to be effected.
- I am fairly sure that my browser, Google Chrome, is not causing it, because it has also happened in Kate and FileZilla.
- When it happens while I am in Google Chrome, it will not just effect the running tab, but all tabs I have open, forcing me to restart Chrome.
- Because the program does not freeze completely, I can still slowly backup my work and just restart the program.

- Both CPU and Memory usage is normal doing the hang up; both swap and ram is well below available.
- Full screen applications do not seem to be effected; I recently played a game in Wine for hours without any issues.

The problem is easily reproducible if I open Kate and edit some text for awhile; it might be related to doing other things at the same time, such as listening to music in VLC Player or on YouTube, but I have not yet confirmed this. (Edit on February 2021: this is not the case. It happens regardless of what I am doing.)

I wonder if there is a way to trace such hang-ups?

This seems related to KDE Plasma.

Edit February 2021:

Okay, since I am still having this problem occasionally, let me just update my main post with new findings.

When the problem happens, you can temporarily unfreeze the affected window by going to compositor -> Tearing Prevention (VSync) = "Never"

Warning: Something behaves weird with Ubuntu 20.04; it appears to auto-update the kernel, which might cause the problem to reoccur silently. It is pretty hard to know it is the same problem, because who checks what kernel they are running? To check your kernel version, write this in terminal:

Code: Select all

uname -r


Last time I tried I got this:

5.7.9-050709-generic

This is a surprise, since I had removed this kernel before. The working kernel version is 5.4.55.

Instead, when you boot the system, make sure to select the working kernel from the boot options menu.

I have not tested the 5.10 version yet.

Two things:

How much RAM and SWAP space do you have?
Do you have enough free space on your disk?

Hi!

From which version did you upgrade? What about the logfiles?

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journalctl -b -xep err  # all errors since boot
journalctl -b -xep 0..4  # errors and warnings

Assuming your i3 is i3wm, not the Intel CPU: How did you set up i3 to work with plasma? Did you disable KWin and use wmctrl?

Another approach is trying out a new created user so that no old config files could mess things up. Does it freeze anyway?

I was just about to respond to your messages when it happened again, and it is very bad timing right now, because I am working on a Website design for a client.

But, just as I had written about my log entries, and a lot of other speculative stuff about what was happening, my browser window started freezing up again. Instead of closing it this time, I decided to carefully investigate while it was happening.

As I mentioned earlier, I am using Google Chrome, and this browser has these three little dots, in the top right corner (the menu).. Now, when I clicked this, I noticed the UI became responsive, very briefly. Then I suspected that maybe it had something to do with the Window Manager, so I went into the Compositor settings and tried setting Tearing Prevention (VSync) to "Never" — as soon as I did that, I instantly regained control over the frozen browser window.

I had previously tried to change to OpenGL 3.0, without it effecting anything. Correctly I have it on OpenGL 2.0 with VSync of Never. Finally, it seems it is as good as new

The fact that it became responsive when clicking the menu is interesting to me, because I basically had a similar problem with my browser a few months back — this was limited to the browser though — only, this was caused by missing glyphs. Here the browser was also "unfrozen" when clicking on the menu. I solved that problem by installing extra fonts focused on emoji's and multi-byte characters. I wonder if that can somehow be related, since normally I think missing glyphs should just be displayed with fall-back characters. Perhaps the compositor was involved back then as well.

Phew.. I was really starting to worry maybe my computer was failing on me haha

Thanks for your time though

It seems like I did not solve the problem very long.

When I change the VSYNC setting, it does not seem to matter what I change it to - it will unfreeze the GUIs and give me back control for a while.
But, at least it is better than shutting down the program completely.

My log files are clean so I have no idea how to trace this bug..

I just installed an older Kernel, the latest in the 5.4 LTS line, and will check if that solves it..

I have now been testing the 5.4.45 Kernel for more than a day, and it appears the problem is fixed.

If anyone else is having the same problem, I would suggest going back to the last LTS kernel. I saw someone mentioning that intel integrated graphics is possibly having problems with the latest kernels..

Currently I am running on Kernel 5.4.45, and it has been very stable.

Not sure if this could be related to temperature caused by kernel. I do not even know what is normal for an intel i3 CPU.. But, I think it was running around 60c on those other kernels — now I got it down at 50c while listening to music in VLC. I remember years ago it was not unusual for intel CPUs to run very hot, without it causing problems though 🤷‍♂️

I will get back if the problem returns, but for now it seems it is solved.

Edit: It is indeed solved. System has been running stable ever since I installed this kernel. I did find out that this is not the latest in the 5.4 line though, the 5.4.55 version is (as of the writing of this); but, I have not tested that one..

August 31 Update: The latest Kernel, version 5.8.0, still has the same problem. Will attempt to move back to latest LTS kernel — for those interested, it can be downloaded from here: https://kernel.ubuntu.com/~kernel-ppa/ubuntu-stable/

I had the same problem while running on the following versions:
Operating System: Garuda Linux
KDE Plasma Version: 5.21.0
KDE Frameworks Version: 5.79.0
Qt Version: 5.15.2
Kernel Version: 5.10.15-120-tkg-bmq
OS Type: 64-bit
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-6700 CPU @ 3.40GHz
Memory: 31,3 GiB of RAM
Graphics Processor: AMD BONAIRE

After reading all the above, and not having the stomach for trying to downgrade my kernel, I opted to take a gamble and simply set my compositor's rendering backend to use OpenGL 2.0 instead of the default OpenGL 3.1.

So far, it seems to be working!


UPDATE
So, with OpenGL 2.0 it still happens from time to time, but for shorter freezes that recover better. I switched back to OpenGL 3.1 but disabled hardware acceleration in Chrome to see what that does.

I'm having the same issue with the entire desktop lagging. Everything I do takes about 3 secs to respond. I changed to OpenGL2.0, but still have the issue and it appears to happen after I make KWIN changes. I always changed the window borders to remember the size and location plus change the border color to Breeze Dark.

I have to reboot to get the desktop to respond normally, but I can replicate the issue again just by making the above mentioned KWIN changes.

Operating System: openSUSE Tumbleweed 20210222
KDE Plasma Version: 5.21.0
KDE Frameworks Version: 5.79.0
Qt Version: 5.15.2
Kernel Version: 5.10.16-1-default
OS Type: 64-bit
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-4810MQ CPU @ 2.80GHz
Memory: 31.0 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 4600

It's happening again. I just made a change to "Show on-screen display when switching" in Virtual Desktops and the problem has started again.

Here is video of the issue.

https://youtu.be/0MCiEpgxzFI

Started with an empty session and that fixed the lag issue, but now I have to get the desktop back to the way I had it.
I'll see if the lag comes back when I make those KWIN changes and desktop effect changes.

Clearing the ./cache(1.5G) did not work. Made the changes and the lag started again.
Here is what I saw in the logs before and after the change.

https://paste.opensuse.org/37976514

2/28/21 5:35 PM systemd Started System Settings - System Settings ---> Lag sarted 2/28/21 5:35 PM kwin_x11 kwin_core: XCB error: 10 (BadAccess), sequence: 14387, resource id: 457, major code: 142 (Composite), minor code: 2 (RedirectSubwindows)

This was in the logs when I logged in and made no changes with no lag.

https://paste.opensuse.org/89754091

It can be like the thread drawing the updates that happen after clicking on stuff is running a million times slower.
Eventually all my queued up clicks eventually get delivered across a range of windows that are visible and I maybe able to move them about (I forget).
My compositor is on OpenGL 2.0 so I will try 3.1 for a time.
And I will switch Tearing Prevention to "Re-use screen content". If you don't hear back maybe it worked.