Bug 504655

Summary: Severe input latency and limited refresh rate option on resolutions other than the native one on kwin wayland
Product: [Plasma] kwin Reporter: q1253328221
Component: wayland-genericAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED FIXED    
Severity: major CC: mira.jary, nate, serdarthtux
Priority: NOR    
Version First Reported In: 6.3.5   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: https://invent.kde.org/plasma/kwin/-/commit/612ec743b30c8a9c38553b6134b92f0de0ae3cad Version Fixed/Implemented In: 6.4.0
Sentry Crash Report:

Description q1253328221 2025-05-22 08:03:21 UTC 
On kwin_wayland if I choose any resolution other than the native resolution ( which is 2560x1600 ), there will be two problems: noticeable input lag and the refresh rate limited 60Hz.

While other setups:
1. on kde plasma on X.org, the refresh rate problem presists, but there's no extra input latency
2. on gnome wayland or windows 11, with resolutions set to below 1600p, there's no extra input latency and i can have 240Hz refresh rate.

Note that on these two platforms there's no 1 second of black screen when changing mode, so i guess that on these two platforms the monitor mode is not changed but mutter (or dwm.exe on windows? i guess) adapts the chosen mode to monitor's native mode. I would love plasma to have an option that it has the same behavior, sometimes i need to lower the resolution to get better performance on some fullscreen games.

Based on the behavior of kde plasma on X mode, I guess that the refresh rate is because of how my monitor reports EDID. But since the input latency problem is unique to kde plasma on wayland, so i guess it's a bug of kwin_wayland.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch linux
KDE Plasma Version: 6.3.5
KDE Frameworks Version: 6.14.0
Qt Version: 6.9.0

Graphics Processor 1: Intel® Graphics
Graphics Processor 2: NVIDIA GeForce RTX 4060 Laptop GPU
Comment 1 Bug Janitor Service 2025-05-22 15:02:31 UTC 
A possibly relevant merge request was started @ https://invent.kde.org/plasma/kwin/-/merge_requests/7667
Comment 2 Zamundaaa 2025-05-23 14:13:43 UTC 
Git commit 6d82dbcb7f344db3e3e772f91ec738b9e431681d by Xaver Hugl.
Committed on 23/05/2025 at 14:13.
Pushed by zamundaaa into branch 'master'.

backends/drm: also generate modes for the native refresh rate of the display

As we only do this when the scaling mode is available, it should be pretty safe,
and these modes avoid driver issues where the refresh rate isn't switched to 60Hz.

M  +122  -81   autotests/drm/drmTest.cpp
M  +20   -13   src/backends/drm/drm_connector.cpp

https://invent.kde.org/plasma/kwin/-/commit/6d82dbcb7f344db3e3e772f91ec738b9e431681d
Comment 3 Zamundaaa 2025-05-23 14:50:05 UTC 
Git commit 612ec743b30c8a9c38553b6134b92f0de0ae3cad by Xaver Hugl.
Committed on 23/05/2025 at 14:50.
Pushed by zamundaaa into branch 'Plasma/6.4'.

backends/drm: also generate modes for the native refresh rate of the display

As we only do this when the scaling mode is available, it should be pretty safe,
and these modes avoid driver issues where the refresh rate isn't switched to 60Hz.


(cherry picked from commit 6d82dbcb7f344db3e3e772f91ec738b9e431681d)

Co-authored-by: Xaver Hugl <xaver.hugl@kde.org>

M  +122  -81   autotests/drm/drmTest.cpp
M  +20   -13   src/backends/drm/drm_connector.cpp

https://invent.kde.org/plasma/kwin/-/commit/612ec743b30c8a9c38553b6134b92f0de0ae3cad
Comment 4 Zamundaaa 2025-05-26 13:40:53 UTC 
*** Bug 483038 has been marked as a duplicate of this bug. ***
Comment 5 Zamundaaa 2025-10-09 19:57:39 UTC 
*** Bug 483038 has been marked as a duplicate of this bug. ***