Created attachment 185426 [details] top and intel_gpu_top SUMMARY Playing a full screen video with Firefox on a 4K display results in > 30% CPU usage by the kwin_wayland process. STEPS TO REPRODUCE 1. Run a video playback in Firefox full screen on a 4K monitor 2. Check 'top' on a second monitor OBSERVED RESULT 'top' shows constant CPU usage of more that 30% EXPECTED RESULT CPU usage should not be so high SOFTWARE/OS VERSIONS KDE Plasma Version: 6.4.5 KDE Frameworks Version: 6.18.0 Qt Version: 6.9.2 ADDITIONAL INFORMATION - The CPU is Intel i5-1135G7, I'm using integrated graphic (Mesa Intel Iris Xe Graphics). - I asked a friend to test this scenario with SwayFX - he had around 4% CPU usage by his compositor. Although he has a different platform - desktop with a dedicated GPU. - If a youtube video isn't opened in full screen the CPU usage by kwin is around 6.5%. - Attaching screenshot with 'top' and 'intel_gpu_top' which I run on the second screen. - I wasn't been able to make 'All Screens' screenshot with Spectacle while a video was playing - the result seems to be corrupted. Probably off topic, but could be related.
Looks fixed in Arch kwin 6.4.5-4. CPU usage in described scenario is ~6%. Would be great to get another confirmation but seems like the bug report can be closed.
I can confirm this with my AMD GPU too. CPU usage is now nice and low, as expected!