Bug 499366

Summary:	Set QSG_NO_VSINK=1 or QSG_USE_SIMPLE_ANIMATION_DRIVER=1 to avoid jerking in some effects
Product:	[Plasma] kwin	Reporter:	Guido <guido.iodice>
Component:	effects-various	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	normal	CC:	guido.iodice, john.kizer
Priority:	NOR
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Guido 2025-01-31 19:05:39 UTC

Ever since switching to QSG for many effects I have noticed that they would occasionally have microshakes, more like a loss of a few frames. Experimenting I found that setting QSG_NO_VSINK=1 solved the problem. Not only that, it seems that this was also related to another problem: when I brought the mouse to the corner of the screen, where I had set the Overview effect, it would start and come back quickly. 

Now it no longer does this. I don't think it is advisable to set QSG_NO_VSINK=1 for the whole environment, my suggestion is to do this only for Kwin within the code. Another approach could be QSG_USE_SIMPLE_ANIMATION_DRIVER=1 which seems to achieve the same result and seems to be preferred in this guide: https://doc.qt.io/qt-6/qtquick-visualcanvas-scenegraph.html

Comment 1 John Kizer 2025-02-05 20:29:54 UTC

Hi - it seems like there is a suggested code change here, along with a description of some undesirable behavior. To help folks address your feedback effectively:

* For a bug report using this Bugzilla ticket, could you please provide the information below about the problem you're experiencing, as requested in the form for entering a bug report?

STEPS TO REPRODUCE
1. 
2. 
3. 

OBSERVED RESULT

EXPECTED RESULT

SOFTWARE/OS VERSIONS
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: 
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 


* If you have a suggested code change, can you please submit that as a Merge Request via KDE Invent (GitLab): https://community.kde.org/Infrastructure/GitLab#Submitting_a_merge_request 

Thanks!

Comment 2 Guido 2025-02-17 14:35:43 UTC

STEPS TO REPRODUCE
1. use the Overview effect often during a session

OBSERVED RESULT
Sometimes is is a bit jerky (few frames drop?)

EXPECTED RESULT
Should be buttery smooth.

SOFTWARE/OS VERSIONS
Operating System: Manjaro Linux 
KDE Plasma Version: 6.3.0
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.14.0-rc3-1-MANJARO (64-bit)
Graphics Platform: X11
Processors: 8 × 11th Gen Intel® Core™ i5-1135G7 @ 2.40GHz
Memory: 15.4 GiB of RAM
Graphics Processor: Intel® Iris® Xe Graphics


> If you have a suggested code change, can you please submit that as a Merge Request via KDE Invent (GitLab): 
Well the change is very trivial, you can do it without change the kwin code. Add QSG_NO_VSINK=1 to the Environment variable in the kwin systemd service.

Comment 3 Bug Janitor Service 2025-03-04 03:46:54 UTC

🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!

Comment 4 Bug Janitor Service 2025-03-19 03:47:19 UTC

🐛🧹 This bug has been in NEEDSINFO status with no change for at least 30 days. Closing as RESOLVED WORKSFORME.