SUMMARY STEPS TO REPRODUCE 1. Do stuff in KDE desktop for a while, perhaps play videos in browser (seems to trigger the symptom with greater probability). OBSERVED RESULT Kwin_x11 eventually and permanently enters "rage state" in which it uses a lot of CPU, grinding on all of my 8 cores and using about 70%-80% of each. EXPECTED RESULT Normal CPU usage. SOFTWARE/OS VERSIONS Operating System: Arch Linux KDE Plasma Version: 5.18.3 KDE Frameworks Version: 5.68.0 Qt Version: 5.14.1 Kernel Version: 5.5.11-arch1-1 OS Type: 64-bit Processors: 8 × AMD FX(tm)-8320 Eight-Core Processor Memory: 15,6 GiB ADDITIONAL INFORMATION - the symptom kicks in after a while - once kwin enters the bad state, it remains in it - while in the bad state, CPU usage can be reduced to normal by disabling desktop effects, but immediately goes up again upon re-enabling them - restarting kwin_x11 while in bad state causes the new kwin_x11 process to enter the bad state immediately - the mildest measure that "cures" the kwin state is logging out and back in - it _seems_ that the bug is more likely to manifest during the first session than after logging out and back in, but this might be a red herring; I haven't tested it enough times to be sure - https://www.reddit.com/r/kde/comments/flc77w/100_thread_usage_by_kwin_x11_nvidia/
We are always improving performance over time as are driver vendors. There is nothing unique in this report that is actionable in itself.