[kde] [Bug 480015] New: KDE Plasma (Wayland) Microstuttering in demanding DX12 games with VRR, perfectly smooth on X11

[bugzilla_noreply at kde.org]

https://bugs.kde.org/show_bug.cgi?id=480015

            Bug ID: 480015
           Summary: KDE Plasma (Wayland) Microstuttering in demanding DX12
                    games with VRR, perfectly smooth on X11
    Classification: I don't know
           Product: kde
           Version: unspecified
          Platform: Arch Linux
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: general
          Assignee: unassigned-bugs at kde.org
          Reporter: mcdarkjedii at gmail.com
  Target Milestone: ---

SUMMARY
***
First of all, apologies if there is already a similar issue open, but I
couldn't find anything similar.

Make sure you're running KDE Plasma on Wayland. Have adaptive sync set to
automatic or always.
Play a demanding DX12 game that supports VRR such as Cyberpunk 2077 & The
Witcher 3.
Make sure the graphical settings are fully maxed out, so you won't exceed your
monitor's refresh rate.
Move mouse around slowly, don't flick it, much easier to do this with an
analogue stick.
There will be visible microstutters.

Compositor set to smoothest animations & lowest latency.
Reduce latency by allowing screen tearign artifacts in fullscreen windows
toggled on and off.
In game settings both Borderless Windowed & Exclusive Fullscreen, Vsync off &
on (slightly reduces stuttering but doesn't eliminate it)
Alt tabbing out and in again. Closing the plasmashell process.
Changing the default Proton/Wine version to GE.
Switching to the Liquorix kernel. Xanmod kernel.
It's less severe in more up to date distros like Arch Linux & Opensuse
Tumbleweed.
Still happening on Arch even when running KDE 6 from kde-unstable repo.
All of these still don't fix the microstutters.

However playing a much less demanding DX12 game like Deep Rock Galactic will be
butter smooth.
Logging in to an X11 Plasma session (with VRR enabled) completely gets rid of
the microstutters.
And if I run Gnome 45 (Wayland) on Arch with the VRR patches for mutter & gnome
control center it will also run smoothly.

***


STEPS TO REPRODUCE
1. Make sure you're running KDE Plasma on Wayland
2. Open a demanding DX 12 game.
3. Turn camera slowly (easiest done with a controller)

OBSERVED RESULT
-Minor stutters, most noticeable when turning the camera at slower speeds.

EXPECTED RESULT
-No visible stutters, butter smooth camera movement. 
Like on X11 or Gnome + VRR patched mutter & control panel.
And of course, Windows 10/11 with Freesync enabled.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Nobara Linux 39
(available in About System)
KDE Plasma Version: 5.27.10
KDE Frameworks Version: 5.113.0
Qt Version: 5.15.11

ADDITIONAL INFORMATION

Kernel Version: 6.7.0-204.fsync.fc39.x86_64 (64-bit)
R7 5800x3d
32GB DDR4 3200Mhz
RX 6800XT
4TB NVMe PCIe 3.0 SSD

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