Created attachment 138987 [details]
dmesg

When amdgpu.dc=1 and an Xorg compositor are enabled at the same time, there is
stuttering when moving windows.
It's most visible with Compton (which is completely stutter-free when
amdgpu.dc=0), but also KWin and to a lesser extent also Gnome-Mutter.
It happens also with GPU clocks forced to maximum, so it doesn't seem to be a
powersaving issue.
In the recent past, there was an issue with performance degrading when
amdgpu.dc=1 and an Xorg compositor are enabled and the hardware mouse cursor
was used, maybe it's still related (just guessing though)?

Tested with Linux 4.17 RC1 and drm-next-4.18-wip (4.16.1.52132fd03)
xorg-server 1.19.6+13+gd0d1a694f (amdgpu DDX & modesetting)
RX 560