On kwin_wayland master, certain screen configurations makes performance (fps) plummet. When my Intel based laptop is using dumb buffers on the Nvidia driven external output(s), certain configs work at 30-60 fps whilst others at 5-15 fps - rendering it virtually unusable. When the Intel screen is placed to the left or to the top in a two monitor config, performance is good. When the laptop screen is placed to the right, to the bottom or cloned, performance hits a brick wall.. The fps kwin effect places itself on the external screen in these instances. Performance used to be decent in any configuration but has definitely worsened with the heavy refactoring of late. SOFTWARE/OS VERSIONS Linux/KDE Plasma: KDE Neon Unstable (available in About System) KDE Plasma Version: 5.22.80 KDE Frameworks Version: 5.86.0 Qt Version: 5.15.3
What do you mean with "with the heavy refactoring of late" / do you have a timeframe of when it got worse?
When you first added 1031 to kwin i was able to watch full screen videos on the external monitor without significant degradation. The past couple of weeks I ave noticed it worsen but wrote it off to having something to do with the troubles I experienced with 1249 and you fixed with 1348. Ever since then the frame rates are all over the place when a secondary display is in use. I even rolled Kwin and KWaylandServer back to 1031 but strangely the fps were super slow. No way i could watch any videos let alone at full screen. The fps drops on both screens simultaneously.
Hmm, if rolling back doesn't work then it must be some other component that changed. Maybe Mesa, or the NVidia driver?
after commit 72af309317b6b5035dd146427b5fc7efebedc222 https://invent.kde.org/plasma/kwin/-/commit/72af309317b6b5035dd146427b5fc7efebedc222 the severe lag previously experienced is gone.
This must be the weirdest bugfix ever - it has absolutely nothing to do with performance and should be completely irrelevant to KWin internals as a whole. I guess we'll just leave it at this, going forward the EglStreams code path will be deprecated anyways.
just to be certain i solely reverted 72af309317b6b5035dd146427b5fc7efebedc222 and the performance degradation was marked. fps is probably not the best metric. they are better with this patch but not extraordinarily however the jagged feeling like frames are being dropped is gone. difference is night and day.