https://bugs.kde.org/show_bug.cgi?id=493090
Bug ID: 493090
Summary: Gamescope using adaptive-sync experiences frequent
jumps to monitor's max refresh rate, not present with
gamescope's own DRM backend
Classification: Plasma
Product: kwin
Version: 6.1.5
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: platform-drm
Assignee: kwin-bugs-n...@kde.org
Reporter: mattschwa...@gwu.edu
Target Milestone: ---
SUMMARY
When using Gamescope's Wayland backend from within a KWin DRM backend session,
adaptive sync in gamescope will often jump up to my monitor's maximum refresh
rate for a small blip before dropping back down to the game's actual frame
rate. VRR recently got a bit of a rework in gamescope as of 3.15.x, and now the
difference between gamescope's DRM backend and nested from Kwin has gotten
noticeable if I look at my monitor's live OSD.
I showed clips of this behavior difference to a gamescope dev and they said the
cause of this was likely happening outside of gamescope itself if gamescope's
VRR was working as expected in the DRM backend. I'll link two videos clips of
the behavior as I'm seeing it on my monitor with gamescope's DRM backend
compared to the nested within the Kwin drm backend along with my monitor's OSD.
---
Gamescope DRM backend command (I use Valve's package that includes
gamescope-session in this case): gamescope -e -h 2160 -w 7860 -r 120
--adaptive-sync --mangoapp -- steam -steamdeck -steamos3 -steampal -gamepadui
Video of behavior w/ gamescope DRM backend: https://youtu.be/CwZpcCX-4V0
Nested gamescope from Plasma command: gamescope -h 2160 -w 7860 -f -r 120
--adaptive-sync --mangoapp -- %command%
Video of behavior w/ gamescope nested on Plasma Wayland:
https://youtu.be/vxfpLZ2b9lI
STEPS TO REPRODUCE
1. Launch a game with a variation of those launch options to fit your display.
Ideally, you want something that will max out the framerate a bit below your
display's refresh rate
2. If your monitor has an OSD that allows you to observe the Variable Refresh
Rate it is processing, enable it.
OBSERVED RESULT
Gamescope with the KWin DRM Backend has many noticeable jumps up to the
display's set refresh rate rather than the game's refresh rate
EXPECTED RESULT
Gamescope with the KWin DRM Backend should have the same VRR behavior as
Gamescope's DRM backend
SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux
KDE Plasma Version: 6.1.5
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
Kernel Version: 6.11.0-rc7-1-cachyos-rc (64-bit)
Graphics Platform: Wayland
Processors: 64 × AMD Ryzen Threadripper 7970X 32-Cores
Memory: 62.3 GiB of RAM
Graphics Processor: AMD Radeon RX 7900 XTX
Gamescope version: gamescope version 3.15.9 (gcc 14.2.1)
ADDITIONAL INFORMATION
No frametime variation is present in the MangoHud overlay
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