SUMMARY After upgrading to the Plasma 6.6 beta, I noticed that in some conditions, I'm getting stutter and/or bad frame timing causing jerkiness. I've noticed this happen in 2 circumstances. One is if I am using Konsole and holding down a key, for example to backspace a large block of text. In this case, the cursor moves jerkily with a different amount of time between each backspace. (The same thing happens if I just hold down the spacebar or any other key to input a large number of characters rapidly.) The second situation is animations in Firefox. For example, if I go to https://lukehaas.me/projects/css-loaders/, the spinners all animate jerkily with kwin 6.5.91 where they were smooth in 6.5.x. Notably, however, scrolling in Firefox and other applications is not affected and remains smooth. This issue also does not seem to affect any game that I have tried, nor does it affect glxgears/vkcube/etc, window dragging, video playback in MPV, or anything else I have tried so far. STEPS TO REPRODUCE 1. Start Konsole 2. Hold down the spacebar OBSERVED RESULT There is a pronounced stutter in the cursor movement; the cursor remains in each position for a different amount of time. EXPECTED RESULT The cursor should remain in each position for the same amount of time and move "smoothly" as it did in kwin 6.5.x and before. SOFTWARE/OS VERSIONS Operating System: Ubuntu 26.04 KDE Plasma Version: 6.5.91 KDE Frameworks Version: 6.22.0 Qt Version: 6.10.2 Kernel Version: 6.19.0-061900rc8-generic (64-bit) Graphics Platform: Wayland Processors: 16 × AMD Ryzen 7 7840U w/ Radeon 780M Graphics Memory: 64 GiB of RAM (60.6 GiB usable) Graphics Processor: AMD Radeon 780M Graphics ADDITIONAL INFORMATION So far I've only tried this with the integrated display and AMD integrated graphics on my Framework 13 (the older 60hz non-VRR one). I haven't had a chance to try it with my 120hz VRR monitor or another system with Intel graphics yet, but I will report here with the results when I do.
Can't repro on KDE Linux, though im on regular desktop PC Operating System: KDE Linux 2026-02-09 KDE Plasma Version: 6.6.80 KDE Frameworks Version: 6.24.0 Qt Version: 6.10.2 Kernel Version: 6.18.7-zen1-1-zen (64-bit) Graphics Platform: Wayland Processors: 12 × AMD Ryzen 5 3600 6-Core Processor Memory: 16 GiB of RAM (15.5 GiB usable) Graphics Processor: AMD Radeon RX 6600 My monitor is 3440x1440@165hz
I did some more testing and found that I could not reproduce it on my 120Hz screen with the same laptop (whether or not Adaptive Sync was enabled made no difference). I also could not reproduce it on another laptop with Intel graphics, which makes me think that the AMD panel self refresh implementation likely has something to do with it. The problem definitely appeared with Plasma 6.5.91 (I never tested 6.5.90) and goes away if I revert to 6.5.5 though.
If you put > KWIN_DRM_OVERRIDE_SAFETY_MARGIN=1500 into /etc/environment, does that help?
Almost forgot to add that you need to reboot for it to apply
That doesn't seem to have any effect. Something I neglected to mention earlier is that it isn't possible to reproduce the issue if I'm also running something like vkcube or even waving the mouse around at the same time.
Okay, that's the only frame timing related thing that changed vs. 6.5. If you also set KWIN_USE_OVERLAYS=0, does that help?
Hmm, that's really odd then. I tried disabling overlays already and that had no effect either. I thought they were disabled by default now anyway?
Overlays are still disabled by default in releases, but not for development and beta versions.
If you set https://invent.kde.org/plasma/kwin/-/wikis/Environment-Variables#kwin_log_performance_data, maybe that will at least show where it's dropping frames. Other than that, likely a bisect is the only way to find out what caused this.
I tried setting KWIN_USE_OVERLAYS=0 again and this time it seems to have cleared up the issue. Perhaps I forgot to reboot the last time or maybe I'm just going crazy. I'm guessing the performance log data is no longer useful. Anyway, it seems this isn't actually a (kwin) bug. Sorry to waste your time.
It's very interesting it causes problems on the 60Hz display but not on the 120Hz one though... Anyways, this was not a waste of time, because I was tempted to enable overlays by default for AMD APUs, and now I'll definitely wait longer until we risk that.
I did some more experimenting and I think what I said in Comment 2 is correct; it is some kind of interaction between PSR and layers. If I have both of those on, I get the issue. If I have either one of them off, I do not get the issue. That of course also explains why I could not reproduce it on the 120Hz screen since that doesn't have PSR.
I've done yet more testing and I'm now pretty sure what I said about the CSS spinners page being jerky is a red herring; it is either caused by the page itself or by Firefox. Other smoothness tests like https://testufo.com/ do not drop frames and the frame drops on the CSS spinners page come and go both with layers on and off. In general, the juddery cursor in Konsole was the only issue I was able to find with layers, and that's a nitpick even by my standards. I couldn't reproduce any of the framedrops that were happening with layers from 6.5.x. And probably no-one else is going to care about the Konsole kursor.
Aaaaand, I just reproduced the cursor jumping with layers turned off. This is a PSR issue and not a kwin issue at all. Please ignore this entire report and accept my apologies.