Bug 505819

Summary:	Plasma 6.4: Stutter in game(s?)
Product:	[Plasma] kwin	Reporter:	mimaro4276
Component:	performance	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	normal	CC:	nate
Priority:	NOR	Keywords:	regression
Version First Reported In:	6.4.0
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description mimaro4276 2025-06-20 05:11:04 UTC

After updating to Plasma 6.4 I noticed periodic sync-like stutter in FFXIV (launched w/ XIVLauncher), reminiscent of the stutter caused by https://bugs.kde.org/show_bug.cgi?id=488843. I haven't noticed it in other games (although I haven't tried very many). This time setting `KWIN_DRM_DISABLE_TRIPLE_BUFFERING=1` doesn't seem to have any effect, so triple buffering itself is not the culprit. Upon disabling triple buffering I did notice slightly less jerky scrolling in e.g. Firefox (might be https://bugs.kde.org/show_bug.cgi?id=490358), but it's not worth the overall loss in system responsiveness.

I also tried using system wine (which is `wine-tkg-git` 10.4 w/ ntsync) and DXVK 2.6.2 instead of the versions provided by XIVLauncher, and it did not make any difference.

Hardware: Hybrid GPU setup (Intel iGPU + AMD dGPU), generic 60Hz monitor w/o VRR

Arch Linux
Kernel: 6.15.2.zen1-1
Mesa: 1:25.1.4-1
Plasma: 6.4.0-1 (from testing)

Comment 1 mimaro4276 2025-06-20 05:26:12 UTC

(In reply to malimach from comment #0)
> Hardware: Hybrid GPU setup (Intel iGPU + AMD dGPU), generic 60Hz monitor w/o
> VRR

I should probably add more detailed hardware specifications just in case:

CPU: i7 3770 w/ Intel HD 4000 (connected to monitor)
GPU: RX 590
RAM: 16GB, 1600MHz
SSD: SATA, 265GB
Monitor: 1080p, 60Hz, VGA

Comment 2 mimaro4276 2025-06-23 17:53:28 UTC

After further testing I found out that the stutter only hapens when running FFXIV through the unofficial AppImage version of XIVLauncher, and the Flatpak versions runs fine, so I suppose this is not a KWin bug. Sorry for the noise.

Comment 3 mimaro4276 2025-06-24 07:51:44 UTC

To be more specific, the stutter seems to occur when XIVLauncher has access to the Wayland socket, regardless of its distribution method. The Flatpak version seems to work because Flatpak allows disabling access to the Wayland socket (and only allowing the x11 one, effectively forcing the use of Xwayland) which the official XIVLauncher Flatpak does by default.