Bug 414245

Summary:	Missing configurations in KWin to prevent shutter and lag.
Product:	[Plasma] kwin	Reporter:	quanticcpu2100
Component:	compositing	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED NOT A BUG
Severity:	wishlist	CC:	nate
Priority:	NOR
Version First Reported In:	5.16.5
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description quanticcpu2100 2019-11-17 19:45:15 UTC

SUMMARY

There are two missing options in the KWin compositor to prevent lag and shutter in fullscreen games without to disable de compositor.

Options ..
1) Sync to VBlank (Only perform screen updates during vertical blanking period)
2) Unredirect Fullscreen Windows (Allow drawing of fullscreen windows to not be redirected to offscreen pixmaps)

EXPECTED RESULT

Able to play games with compositor ON and without shutter and more fps.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 31/Plasma 5.16.5
(available in About System)
KDE Plasma Version: 5.16.5
KDE Frameworks Version: 5.61 
Qt Version: 5.12.5

ADDITIONAL INFORMATION

It appears that when you are using compositor, Nvidia X Server settings' Vblank option does not work. If you are using compositor then select the sync to VBlank can help fix this issue. VBlank is useful for watching videos and playing games "screen tearing" which is horizontal lines occasionally distorting videos. Enabling Sync to VBlank will usually fix the screen tearing issues.

Comment 1 Christoph Feck 2019-11-18 22:56:33 UTC

Please don't assign bugs to yourself, unless you also describe how you intent to fix them.

Comment 2 quanticcpu2100 2019-11-19 03:19:02 UTC

(In reply to Christoph Feck from comment #1)
> Please don't assign bugs to yourself, unless you also describe how you
> intent to fix them.

The two required features are described above.

Comment 3 Vlad Zahorodnii 2019-11-20 14:22:38 UTC

KWin syncs to vblank, sort of, and there is an option to control whether it needs to do that.

You want to have as less as possible stuff going on between the game and its pixel data getting on the screen. Syncing to vblank won't improve performance and won't increase fps.