Bug 419252

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/