https://bugs.kde.org/show_bug.cgi?id=520806
Bug ID: 520806
Summary: Regular frame pacing stutters with fractional scaling
on Wayland when multiple monitors are active
Classification: Plasma
Product: kwin
Version First 6.6.5
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: multi-screen
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 192723
--> https://bugs.kde.org/attachment.cgi?id=192723&action=edit
Kwin support information
On Wayland, enabling fractional scaling (tested with both 125% and 150%) causes
regular frame pacing stutters across the entire desktop when two monitors are
active.
The issue is not limited to games. It can be reproduced during normal desktop
usage, for example by using Firefox middle-click autoscroll and observing
periodic microstutters while scrolling. Games make the issue more noticeable
because the frametime spikes are easier to see.
The stutters occur approximately every 1-2 seconds and are visible in both
native Vulkan and DX12 games, as well as regular desktop applications.
The issue disappears immediately when:
Display scaling is set to 100%
The secondary monitor is disabled via kscreen-doctor
The secondary monitor is physically disconnected
An additional observation is that the stutters also disappear when both
monitors have fullscreen applications displayed simultaneously. For example, if
a game is fullscreen on one monitor and another application is fullscreen on
the second monitor, frame pacing becomes smooth again.
The issue persists when:
both monitors have same refresh rate
plasmashell is terminated
Direct scanout is disabled using KWIN_DRM_NO_DIRECT_SCANOUT=1
Operating System:
Fedora Linux 44 (Wayland session)
Kernel:
7.0.10-201.fc44.x86_64
Desktop Environment:
KDE Plasma 6.6.5
Graphics Hardware:
Sapphire Radeon RX 9070
Graphics Stack:
amdgpu kernel driver
Mesa 26.0.7 (also tested on Mesa-git 26.1.1)
Display Configuration:
DP-1: Xiaomi Mi Monitor, 2560x1440 @ 180 Hz
DP-2: AOC 24G2W1G4, 1920x1080 @ 144 Hz
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