Created attachment 139436 [details] Xorg log I've noticed that moving around windows and scrolling seems to stutter when running at 75 Hz on my monitor. When moving back down to 60 Hz it is completely smooth. In fact, 60 Hz looks smoother, while 75 looks like it is skipping frames. In Windows however it is completely smooth at 75 Hz. This occurs on a Radeon Pro WX 7100. The other thing I noticed... is that when I run at 75 Hz I get artifacts all over the desktop, which show up as flashing blue lines. This behavior is exhibited on all AMD GPUs I own (also tested with a RX Vega 64), so it's not a faulty card. I found that it is fixed by forcing the performance profile to high, like so: echo high > /sys/class/drm/card0/device/power_dpm_force_performance_level I attached my Xorg log. I'm running the 4.16.6 kernel. Full specs: Threadripper 1950X 64GB RAM WX 7100 LG 38UC99 monitor
Something else that may be of note: Setting amdgpu.dc to 0 sort of fixes the stutter and general performance issues I'm seeing. Also there is no flickering/artifacts after a fresh boot, without touching the performance level setting. It isn't 100% though, after some time the desktop will start stuttering again when moving windows around. But right after a fresh boot, or switching resolutions, it is completely smooth, as it should be. In this mode however I notice the cursor skips frames. With amdgpu.dc=1 the cursor never skips frames. All in all, neither mode is usable for me and I've resorted to using HDMI on my monitor which locks the refresh at 60 Hz.
This could be at least somewhat related to bug 106175. There seems to be a bad interaction between HW cursor movement and page flips with DC.
Maybe the artifacts with 75Hz are related to my problem I have with 75Hz WQHD via DL-DVI? https://bugs.freedesktop.org/show_bug.cgi?id=105300 However, with 72Hz and amdgpu.dc=0, my desktop is always 100% free of stutter artifacts (without heavy load on CPU and GPU) with my RX 560.
tempel.julian: Yeah I think the artifacts I'm getting 75 Hz are related. I tried creating a custom resolution @ 70 Hz and the artifacts went away completely without having to change the performance profile setting. The window stutter seems to be something else. I tried the PageFlip setting to false as mentioned in another thread but that did not fix it for me. At 70 Hz there's less stutter too though, not as noticeable as it is at 75. It might be something to do with the monitor. I read in a review that the 38UC99 frameskips even in Windows when FreeSync is OFF. So could the issue be that Linuux doesn't have full FreeSync support yet? I tested in Windows with FreeSync off, and it does stutter in a similar way. Although, the cursor also stutters. The cursor doesn't stutter at all in Linux, as long as FreeSync is ON, so it does seem to be doing something. I'm not sure how to really debug this further though.
Created attachment 140058 [details] dmesg
Have you tried using the amdgpu.dpm=1 kernel command? It's worked for me with my 390X.
Adding amdgpu.dpm=1 did not fix it, unfortunately. Noticed no change on my WX7100. Thanks for the suggestion though.
Did some more testing, this time with a Nvidia card to see if the issues occurred there and with a different DE. I now think the stuttering I'm experiencing is purely a Gnome issue. I gave KDE a try and 75 Hz is completely smooth, just like in Windows. I also tried the 1080 Ti in Gnome and it had the same stuttering my WX7100 and Vega 64 have. The artifacts definitely seem to be AMDGPU related though. The 1080 Ti doesn't artifact at all when running at 75 Hz.
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