https://bugs.kde.org/show_bug.cgi?id=382478
Bug ID: 382478
Summary: Tearing with Nvidia and performance drops with new
windows
Product: kwin
Version: 5.10.4
Platform: Archlinux Packages
OS: Linux
Status: UNCONFIRMED
Severity: normal
Priority: NOR
Component: compositing
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
No vsync option offered by the Compositor UI dialog is actually able to fix the
tearing with Nvidia (GTX 1070 and 382.22). After the first seconds when KWin is
done with initializing (or whatever it does during the fist seconds when moving
windows is stuttery), the tearing will occur.
There are three possibilites to get compositor's vsync working, but they all
come with a drawback:
1.) __GL_YIELD="USLEEP". This reduces CPU performance a bit in games, also with
deactivated compositing.
2.) KWIN_TRIPLE_BUFFER=1. This introduces stuttering and breaks vsync in
certain OGL applications like Firefox.
3.) Option "TripleBuffer" "1". According to spec, this lets the driver enforce
TB for every application (also if just DB is desired) and it leads to the same
drawbacks as 2.).
Combining 2 & 3 doesn't achieve anything better.
There is also the ForceCompositionPipeline setting for the Nvidia driver, but
this is just a hack which introduces latency and costs GPU performance.
So, 1.) is the least evil. But it's not optimal though, users need to mess
around with config files and suffer a CPU performance penalty.
Is it really not possible to get proper vsync with KWin for free?
--------------
Second issue:
The Nvidia driver has a performance problem with X when new windows open. Just
let KWin draw the compositing fps and open new windows or context menues: The
fps rate will drop for a short time. This also happens with disabled
compositing.
Is there some chance that KWin compositing can improve this?
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