Bug 492051

Summary:	GPU underutilization on Star Citizen (vulkan)
Product:	[Plasma] kwin	Reporter:	Bernard <w.iron.zombie>
Component:	performance	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	REPORTED ---
Severity:	normal	CC:	gort818, nate
Priority:	NOR
Version First Reported In:	git master
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	Star Citizen KWin Wayland vs X11 comparison

Description Bernard 2024-08-22 22:31:48 UTC

SUMMARY

When running star citizen with its vulkan backend on kde with wayland, the framerate varies from 50 to ~70, despite vsync being disabled, and putting the game in fullscreen mode doesn't fix it.
Xwayland is most likely not the culprit as I remember trying wine's wayland backend a while ago and running into the same problem.
As seen in the .gif attachment, there is no such issue on x11, and according to a few other people in the SC linux community it doesn't happen on other desktop environments or window managers.

STEPS TO REPRODUCE
1. Launch star citizen with wine-staging
2. Set backend to vulkan
3. Restart
4. Join an offline arena commander free flight server for testing
4. Observe

OBSERVED RESULT

The GPU is underutilized and never gets past 75% no matter what

EXPECTED RESULT

Full GPU usage like on x11

SOFTWARE/OS VERSIONS
Linux: Gentoo 2.15 / Kernel 6.10.6
KDE Plasma Version: master
KDE Frameworks Version: master
Qt Version: 6.7.2
Wine: staging 9.15 with ntsync patch

ADDITIONAL INFORMATION
Also happens on stable KDE
Output of "qdbus6 org.kde.KWin /KWin supportInformation": https://invent.kde.org/-/snippets/3207

Comment 1 Bernard 2024-08-22 22:36:38 UTC

Created attachment 172863 [details]
Star Citizen KWin Wayland vs X11 comparison

Comment 2 Alessandro 2024-08-23 01:39:24 UTC

I can also reproduce this on Arch.

For now I  am using gamescope as a workaround to bypass kwin, I now get over 95% GPU utilization and much high frame rates when using the wayland session.

Comment 3 Bernard 2024-10-12 12:10:04 UTC

I tried star citizen's PTU build today and apparently pausing and unpausing the game now gets rid of the underutilization issue but it's still happening before then

Comment 4 Bernard 2024-10-15 19:35:55 UTC

(In reply to Bernard from comment #3)
> I tried star citizen's PTU build today and apparently pausing and unpausing
> the game now gets rid of the underutilization issue but it's still happening
> before then

Oopsie, forgot to mention that I did this testing with the DirectX backend & not the Vulkan one
So now in SC 3.24.2 it will affect both backends (haven't tried vulkan again as it is currently completely broken on that testing version but I'd assume it will still happen)