When I first log in, I experience tearing, even though I have vsync enabled. If I change the vsync type option, apply it, and then disable and re-enable desktop effects, the tearing goes away.
Maybe there is some code that is run when changing the vsync type that should also be run when kwin initially starts up, but isn't for some reason.
Steps to Reproduce:
1. Log in.
2. Observe tearing.
3. Change System Settings -> Desktop Effects -> Advanced -> OpenGL Options -> Tearing Prevention (VSync) option.
4. Disable desktop effects.
5. Re-enable desktop effects.
6. Observe that tearing is gone.
There is tearing.
As I have vsync enabled, there should not be tearing.
GeForce GTX 670
NVIDIA proprietary driver version 331.49
Please post the output of:
grep -i triple /var/log/Xorg.0.log
cat /proc/`pidof kwin`/environ
See bug #322060
There seems a redetection error about the availability of triple buffering, so you might end up with vsync *invalidly* being enabled.
The grep command yields no output.
activating vsync is actually a bug (improper redetection after reconfigure)
do you get "higher" cpu load with working vsync (and no triple buffering nor usleep yielding)?
*** This bug has been marked as a duplicate of bug 322060 ***
kwin uses very little cpu power when vsync is working, but I haven't checked it when broken to compare; I'll do that when I get a chance.
No perceptible difference in cpu load between before and after.
Using usleep yielding (through a script in ~/.kde4/env) does workaround the problem for me, and doesn't seem to cause any more cpu load, at least as far as I can tell; haven't tested extensively. I'm going to keep that for now, so I'll report if I notice any problems.
By the way, issue still exists on kwin 4.11.7 and nvidia driver 334.21.
(Sorry for posting in the dup bug, if that's not what you wanted me to do. I'm just replying here because you asked here. I'll post in the main bug in the future if anything changes.)
If at all, yielding usleep is supposed to lower the CPU load (for double buffering)
It's ok to post to the bug, it's yours ;-)