https://bugs.kde.org/show_bug.cgi?id=513397
Bug ID: 513397
Summary: Desktop-wide stuttering when resizing certain Wayland
clients
Classification: Plasma
Product: kwin
Version First 6.5.4
Reported In:
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
When resizing certain Wayland clients, there are some desktop-wide stutters
visible, especially at 200% display scale. This does not affect some clients,
like Chromium, Zed (IDE), Signal, EasyEffects (the new Qt/Kirigami UI), when
launched using their Wayland backends or X11 applications.
STEPS TO REPRODUCE
1. Use a high-resolution monitor (preferably 2160p) and set its scaling to 200%
2. Open https://www.vsynctester.com in Chromium (Firefox is unfortunately not
suitable for this test) or a similar adequate presentation measuring tool
(weston-presentation-shm will work too but it could be a bit harder to see the
issue there)
3. Keep the graph and the scrolling image visible
4. Open an affected app and make sure it's a Wayland client, not an X11 one
(i.e. Firefox, GIMP3, OBS Studio, qBittorrent, I have compiled a more complete
list at the end)
5. Resize it in a fast way for a while, try to make the window as large as
possible too
OBSERVED RESULT
The graph shows severe frame time fluctuations and the scrolling image
stutters, especially when resizing large windows, it's less problematic with
smaller ones but still visible nonetheless
EXPECTED RESULT
Nothing stutters at all, like with the unaffected apps listed below
SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 6.5.4
KDE Frameworks Version: 6.21.0
Qt Version: 6.10.1
Kernel Version: 6.18.1-arch1-2 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 5800X 8-Core Processor
Memory: 64 GiB of RAM (62.7 GiB usable)
Graphics Processor: AMD Radeon RX 9070
Displays: 3840x2160@160Hz at 200%, 1920x1080@120Hz at 100%
ADDITIONAL INFORMATION
My hypothesis is the clients that don't cause stutter are fully GPU
accelerated, whereas those that do are mostly CPU-rendered, but OBS Studio
might disprove that if it's fully GPU accelerated too (it crashes on a GPU
reset but that might only be due to the preview part).
I have compiled some app data as well.
Apps that cause stutter when resizing:
- Firefox
- GIMP3
- Thunderbird
- PulseAudio Volume Control (Qt)
- OBS Studio
- qBittorrent
- qpwgraph
Apps that don't cause stutter no matter how large their windows are at the time
of their resizing:
- Zed (IDE)
- EasyEffects (here only the app window is laggy when resizing, but it doesn't
affect anything else)
- pwvucontrol
- Chromium
- signal-desktop or any Electron/CEF app (with --ozone-platform=wayland)
- X11 applications, even if their resizing is slow
Previously I thought my RX 6600 XT was too weak for 2160p for some reason but
now that my new 9070 does the same thing it obviously can't be that.
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