Bug 343773

Summary:	kwin_x11 does not paint windows, uses 100% CPU in OpenGL mode, under NVidia Legacy driver 304, GeForce 7025 / nForce 630a
Product:	[Plasma] kwin	Reporter:	sombragris
Component:	compositing	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	major	CC:	adloconwy+kdebug
Priority:	NOR
Version:	5.2.0.1
Target Milestone:	---
Platform:	Slackware
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description sombragris 2015-02-04 13:57:15 UTC

Hi,

I use a motherboard whose video chip identifies in lspci as GeForce 7025 / nForce 630a. I have to use the latest nVidia 304.125 legacy driver, because the nouveau driver is not an option (random hard lockups/freezes).

If the rendering engine in KWin is one of the OpenGL variants (2.1, 3.0), Plasma starts but doesn't complete the startup sequence. Looking at htop shows that a process identified as kwin_x11 consumes 100% of CPU.

Killing kwin_x11 gives a desktop without window manager. I can open applications, but all of them without window decorations and uniformly placed at the top left corner of screen.

Changing the rendering engine to XRender works around the problem and gives me an usable desktop.

Thank you, 

Eduardo

Reproducible: Always

Steps to Reproduce:
1. Select any kind of OpenGL rendering for KWin.
2.
3.

Actual Results:  
Kwin does not show at startup, uses 100% of CPU.

Expected Results:  
Kwin should start and work properly.

Comment 1 Thomas Lübking 2015-02-04 14:30:26 UTC

please try
 KWIN_EXPLICIT_SYNC=0 kwin_x11 --replace &
to confirm the duplicate.

*** This bug has been marked as a duplicate of bug 343551 ***

Comment 2 sombragris 2015-02-04 17:31:45 UTC

Trying KWIN_EXPLICIT_SYNC=0 kwin_x11 --replace & and got the following results:

a) With XRender: No change.
b) With OpenGL 3.1: limited desktop effects, some rendering artifacts (metallic grey on transparent surfaces, etc), but otherwise it works.
c) With OpenGL 2.0: Works, all desktop effects function, rather slow but OK.

b) and c) were observed with GLX as rendering interface.

Thank you for the suggestion. How can I enable this so kwin would start this way every time by default?

Comment 3 Thomas Lübking 2015-02-04 18:04:31 UTC

adding a file ~/.config/plasma-workspace/env/kwin.sh with the content

#!/bin/sh
export KWIN_EXPLICIT_SYNC=0

should do.

Don't forget to make is executable
    chmod +x ~/.config/plasma-workspace/env/kwin.sh

NOTICE:
that I don't know whether this path will change in future (the startkde script has some unspecific comment about this)

Nvidia does not support egl on X11 atm (and I doubt the legacy driver ever will)
Speed could be driven by misdetected triple buffering support, bug #343184

Comment 4 sombragris 2015-02-05 11:24:51 UTC

Thank you Thomas!

Comment 5 adlo 2015-05-09 01:37:55 UTC

This bug still seems to exist in Plasma 5.3 on Arch Linux.