https://bugs.kde.org/show_bug.cgi?id=493745
--- Comment #2 from Khanich <khanich.opensou...@gmx.de> --- (In reply to Zamundaaa from comment #1) > Gaming on external GPUs is indeed very challenging. By default, what happens > is that > 1. the app renders on the external GPU. Because of limited bandwidth of the > USB C connection and https://gitlab.freedesktop.org/mesa/mesa/-/issues/7340, > performance is worse compared to having it in a 16x PCIe slot > 2. the driver copies the rendered results to a buffer in system memory > 3. KWin gets that buffer in system memory, composites a results with the > integrated GPU > 4. KWin either presents the composited result directly, or copies the > composited result back to the eGPU and presents it on a display connected to > that > > There are efforts to fix that > (https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/ > 268), but none of this has changed in any way in the last few years. > Well, hopefully there won't take as long as many other protocols did. > > While trying to run a game fullscreen the eGPU gets used as expected (at > > least according to radeontop), but I don't see a picture, just a black > > screen > That sounds like a problem we can investigate though. If you put > KWIN_DRM_NO_DIRECT_SCANOUT=1 into /etc/environment and reboot, does anything > change in regard to that? I just tested it with this variable in /etc/environment with both a Proton game (Farming Simulator 22 with Proton version 9.0-3) and a native game fullscreen (War Thunder again) and it works. So, the black screen apparently is a bug in KWin's direct scanout implementation I guess? I also decided to do the same test in War Thunder in windowed mode again with this variable and without (because a Patch on the side of WT could have changed this after all and I think I saw a MESA update in the last few days, although I am not sure; besides, it makes thinks more comparable): With variable on internal monitor: ~60 With variable on external monitor connected to the eGPU where the game runs: ~55 Without variable on internal monitor: ~45 Without variable on external monitor connected to the eGPU where the game runs: ~40 I am not sure, but should this be the case in windowed mode? -- You are receiving this mail because: You are watching all bug changes.
