[Bug 106175] amdgpu.dc=1 shows performance issues with Xorg compositors when moving windows

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106175

--- Comment #53 from bmilreu at gmail.com ---
(In reply to rropid from comment #45)
> (In reply to bmilreu from comment #43)
> > If devs want an easy test case, use these links for reproducing it in
> > chromium:
> > 
> > https://www.vsynctester.com/
> > https://www.testufo.com/photo
> > https://www.slither.io
> > 
> > move the cursor around, move/resize some windows. you will notice it
> > 
> > the vsync/cursor stutters and frame-skips are pretty noticeable with dc=1 on
> > all three links
> > 
> > KWin, compton, TearFree, mutter, xfwm4 all have the same problems.
> 
> I just tried dc=1 and I only seem to have a problem if I use TearFree.
> Things are totally fine without TearFree.
> 
> To be clear about what I'm doing here right now:
> 
> I made sure DC is enabled:
> 
>   $ systool -vm amdgpu | grep dc
>       dc                  = "1"
>   $ dmesg | grep -i display
>   [    1.014297] [drm] Display Core initialized with v3.1.59!
> 
> I removed TearFree from my X config:
> 
>   $ cat /etc/X11/xorg.conf.d/20-amdgpu.conf 
>   Section "OutputClass"
>       Identifier "my amdgpu settings"
>       MatchDriver "amdgpu"
>       Option "DRI" "3"
>   EndSection
> 
> And I started Compton like this to make sure it's a clean config:
> 
>   $ compton --config /dev/null --backend glx --vsync opengl
> 
> With this setup, I don't seem to have any stutter. I visited the websites
> you mention in a Chromium window, then opened another window and tried
> moving things around and resizing. It behaves fine, same as what I know from
> normally using dc=0.
> 
> Kernel is 4.19.2, Mesa 18.2.4, Xorg 1.20.3, the GPU is a RX480, monitor is
> 60 Hz.
> 
> After I had typed this, I have now added TearFree to the X config and
> restarted X:
> 
>   $ cat /etc/X11/xorg.conf.d/20-amdgpu.conf 
>   Section "OutputClass"
>       Identifier "my amdgpu settings"
>       MatchDriver "amdgpu"
>       Option "TearFree" "true"
>       Option "DRI" "3"
>   EndSection
> 
> Now, with TearFree enabled, things are super terrible. Trying to move a
> window around has extreme stutter, it seems to drop frames. If I restart
> Compton with "GALLIUM_HUD=fps" and then try moving a window around in
> circles, I can see it stays below 40 fps instead of hitting the 60 fps that
> it should be running at.

"compton --vsync opengl" is a case less/not affected by this in my setup, try
--vsync opengl-swc, --vsync opengl-oml or --vsync opengl-mswc

Also try other compositors. Kwin, mutter, xfwm4

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