Created attachment 143989 [details]
corruption when starting blender benchmark
When I start the Blender benchmark, I usually get brief corruption like shown in the attached picture.
This probably is what I mentioned in this ticket as a sidenote:
Happens with both amdgpu DDX and modesetting.
Tested with altest xserver-git and xf86-video-amdgpu-git.
Benchmark can be obtained from here:
Forgot to mention: Happens with and without compositor.
(In reply to tempel.julian from comment #0)
> Happens with both amdgpu DDX and modesetting.
That indicates against it being an xf86-video-amdgpu bug then. It sounds like a blender or Mesa issue most likely.
I can't seem to reproduce. Please attach the corresponding Xorg log file and output of dmesg and glxinfo.
Created attachment 143994 [details]
Created attachment 143995 [details]
Created attachment 143996 [details]
Seems to happen less likely with KWin than with Compton or no compositor.
My guess as a layman would be that the program initializes GL rendering inside the window, but freezes for a moment while doing so and then shows the artifacts until it is done initializing.
In that case it would be nice if the mesa/xorg infrastructure could prevent such artifacts, instead of expecting of the program to initialize without interruption, as there always will be such edge cases.
At least I'm not aware of similar artifacts on the Windows platform.
Can you try if this also happens with Mesa 19.0 or older?
I was able to reproduce it after all, and upon inspection with apitrace and gdb, it's indeed a blender bug. It calls glXSwapBuffers without drawing anything to the back buffer before, which is basically like asking "please put up random stuff as the window contents".
Thanks for looking into it. Is it possible for xorg/mesa to just show solid black instead of "modern art" in such cases?
Of course not an important matter at all, compared to other things like xwayland fake 60 Hz windowed behavior etc. :)
(In reply to tempel.julian from comment #9)
> Thanks for looking into it. Is it possible for xorg/mesa to just show solid
> black instead of "modern art" in such cases?
Xorg can't know that the client really wanted to present something else than what it asked to present. :)
Mesa might be able to work around this, but I'm not sure it's worth it or even a good idea.