%cpu and Xorg - Jaunty

[Mark Greenwood]

On Friday 03 April 2009 15:49:43 Dotan Cohen wrote:
> > Without Desktop effects enabled and the new (today's) updates, Xorg seems to be behaving. If
> > however I switch Desktop effects back on then my cpu usage goes back up.
> 
> As you have reproduction instructions, file it!
> 
> -- 
> Dotan Cohen
> 
> http://what-is-what.com
> http://gibberish.co.il
> 
I'm almost certain that this is a video driver issue. Are you using nvidia drivers? I am. I found two things:

Disabling 'use Vsync' on the Advanced tab under Desktop Effects helped a little

Also, I created /etc/modprobe.d/nvidia.conf which contains one line

options nvidia NVreg_EnableMSI=1

You need quite recent hardware for this to work, but it enabled 'Message Signalled Interrupts' for the nvidia driver (180.44), which stops it from sharing interrupts with any other hardware. You can find out f it worked by doing

cat /proc/interrupts

You should see

2294:        309        104   PCI-MSI-edge      nvidia

(the numbers will be different). 

Please note, I don't know what effect this will have if your hardware doesn't support MSI. It may make it impossible for you to start KDE.. Anyway, it didn't cure the problem for me but it has helped reduce CPU usage of Xorg and kwin, and the desktop does feel a little more responsive.



Mark