Comment 73 for bug 1222602

I'm not sure if this fits into this particular bug, but maybe it helps to locate the problem...

I have a netbook with Intel Atom N455 and GMA3150. The netbook has an external monitor attached to it via a KVM switch (USB mouse and keyboard, VGA) and has run Ubuntu since 11.10 (13.10 upto yesterday and now 14.04). The dual monitor setup has worked for nearly 2,5 years without any real issues.

A few days ago, the external monitor broke. It was an old Samtron CRT which I ran at 1152x864/75 Hz. I got a new monitor, a LCD flatscreen with 1366x768, to replace it.

Booting with the new monitor works. It shows the plymouth screen, LightDM's login screen and also Unity. But compiz now eats roughly 50% of the CPU as reported by top, and all graphical effects are utterly slow. This happened under 13.10 and now with 14.04 as well, with all updates installed.

I've tried the things mentioned above and some others I've found while searching for this bug:

- Renamed ~/.compiz folder. That actually worked once, but the high CPU usage was back after a reboot. Didn't do anything when I tried it again.

- Disabled "sync to vblank" in CCSM. Didn't do anything.

- CCSM -> Preferences -> Reset Unity profile. Worked, but high CPU usage was back after a reboot.

- Set MESA_GL_VERSION_OVERRIDE=1.4 in /etc/environment. Didn't do anything.

- Installed the latest packages from Oibaf's PPA. Didn't do anything.

- Guest session instead of my regular account. Had high CPU usage as well.

I then decided to install 14.04, hoping the bug would be fixed. Unfortunately, it's still there.

BTW, "/usr/lib/nux/unity_support_test -p" shows (under 14.04):

--------8<--------
OpenGL vendor string: Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) IGD
OpenGL version string: 1.4 Mesa 10.1.0

Not software rendered: yes
Not blacklisted: yes
GLX fbconfig: yes
GLX texture from pixmap: yes
GL npot or rect textures: yes
GL vertex program: yes
GL fragment program: yes
GL vertex buffer object: yes
GL framebuffer object: yes
GL version is 1.4+: yes

Unity 3D supported: yes
--------8<--------

I had "yes" everywhere under 13.10 as well, with both default mesa from the Ubuntu repositories and the version from Oibaf's PPA.

Yesterday, after installing 14.04 and re-installing my favourite software packages, I got a few updates. Two dozen packages or so, including the "3.13.0-20-generic #42" kernel. I installed those and rebooted. After logging in, THE HIGH CPU USAGE WAS GONE. But after another reboot, compiz ate half the CPU again. Huh???

Anyway, I've now found a "solution". Well, not really, but it works for now until the problem is properly fixed. I simply unplug the KVM switch's USB cable before booting to prevent the external monitor from being seen by the system. Once I'm logged in into Unity, I plug the KVM switch back in, then the external monitor turns on, the internal one turns off (as it should), and everything works as expected, without high CPU usage or slow graphical effects.

I hope this helps someone.