SUMMARY
After upgrading to Plasma 6.4.90, I have noticed that I randomly but rather often seem to get jerkiness or framerate drops to 30fps for a few seconds which are usually most noticeable due to jerky mouse cursor movement.  This seems to happen most often after opening new windows, particularly Firefox windows.  I've only noticed this on a PC with AMD graphics; I cannot seem to reproduce it with Intel graphics.  It also seems to happen less severely if I put the GPU in "game mode" in the UEFI config (which just increases the static VRAM allocation).

For reference, the system is a Framework 13 laptop with the AMD 7840 processor and the 780m GPU.  I reproduced the issue while driving a single 3840x2160p60 monitor.  With Plasma 6.4.5, I never saw this behavior and everything was always smooth.

STEPS TO REPRODUCE
1. Run kwin 6.4.90 on a system with AMD integrated graphics in "auto" memory allocation mode
2. Open and close Firefox windows
3. Wave the mouse around for a bit after opening/closing each window

OBSERVED RESULT
Often frames will drop or the framerate will drop to 30fps for a few seconds.

EXPECTED RESULT
The framerate should remain at 60fps without dropping frames.

SOFTWARE/OS VERSIONS
Linux: 6.17.0-061700rc7
KDE Plasma Version: 6.4.90
KDE Frameworks Version: 6.18.0
Qt Version: 6.9.2