Dolphin and other KDE applications suddenly start to slow down

Hello everyone,

I’m looking for some help to solve or identify a problem with KDE.

I currently use the latest LTS version of Ubuntu 22.04 with KDE :

  • plasma-desktop : 4:5.24.7-0ubuntu0.1
  • konsole, dolphin, gwenview, kate : 4:21.12.3-0ubuntu1

I only use the machine from remote sessions via the VNC.
tigervnc-standalone-server : 1.12.0+dfsg-4

When I start a new VNC session with a KDE environment, everything works properly.

After a time of use that can vary from a few minutes to several days, Dolphin suddenly slows down. It will then take more than 15 to 20 seconds to open it. Navigating within directories becomes extremely slow (10-15 seconds between the click and the reaction). The scroll also becomes very slow.

If I open a second VNC session, this slowness also affects my new screen. But other users on the computer don’t have this problem at the same time. Although this can happen to them also but not at the same time. Dolphin can therefore be very slow for only a user.

The only solution is to kill all the processes that belong to the user and to relaunch a new session, and there the problem disappears.

When I detect a big slowdown of Dolphin, other KDE applications such as Gwenview and Kate also become extremely slow. On the other hand, the starting menu of KDE is still operational, and doesn’t seems to be impacted.

I’ve been using KDE for a while on a laptop and I’ve never met this kind of problem. The only difference here is that this machine mounts NFS shares via autofs.
But this does not seem to be the real source of the problem because it is quite possible to continue to use and browse NFS shares without any issues with other applications such as Konsole, Libreoffice, …

I can’t find anything that can help me in system log files, or in session logs or VNC server. No
error to be noted when I launch dolphin from a command line.

Do you have ideas to solve or at least identify the source of the problem to make a bug report?

Thank you in advance for your help.