On my systems the refresh rate drops significantly while a plasma notification is shown on the screen so that the system feels super slow then. I don't know the boundary condition, but I can describe some way where at least I can somehow observe and reproduce it. STEPS TO REPRODUCE 1. I have a Spotify instance open (flatpak) 2. I have a Firefox instance open 3. Open a Website in Firefox and scroll threw it (works fine) 4. Change the title, so that a notification is shown 5. Scroll the website while the notification is present: It is stuttering until the notification has purged (I was also able to make that happen with a notification caused by a "ping" from the mobile in kde connect instead of Spotify and observed the stuttered scrolling also e. g. in Dolphin. Also videos are stuttering while a notification is present on screen.) OBSERVED RESULT System is stuttering EXPECTED RESULT System should stay smooth SOFTWARE/OS VERSIONS Linux/KDE Plasma: openSUSE Tumbleweed 20210626 (available in About System) KDE Plasma Version: 5.22.1 KDE Frameworks Version: 5.83.0 Qt Version: 5.12.2 Kernel 5.12.12-1 X11 GeForce GTX 1070 If this could be a reproduction criteria: widescreen Display with high resolution (5120x1440) Addition: Sometimes I have the feeling that a similar slow down is observed when starting new apps. But there I have difficulties to reproduce up to now...)
You can simulate notifications by using $ notify-send foo bar Does this also happen with composting disabled? Does it happen with blur and contrast effects disabled?
I tested what you suggested: - With compositor disabled it does not happen. - Before changing Blur and Background contrast settings: They have a "semi-ticked" state in my system settings. What could that mean? Could that be some state from a older version which causes trouble? https://cloud.10hoch-6.de/index.php/s/ZoMSgffs6NzFyz7
*** This bug has been marked as a duplicate of bug 414785 ***