Comment 9 for bug 653851

In my case it seems like the problem is high interrupt load due to ACPI. I still do not understand what exactly ACPI has to do with Xorg CPU Utilization, it is even stranger that an ACPI problem could cause high CPU utilization for user applications like gedit or thunderbird, but the fact is that once I added acpi=off to Kernel Boot, the Xorg, gnome-panel, gedit, thunderbird CPU utilization were scaled to more reasonable levels and the GUI become much more responsive.

Turning of ACPI disables many important functions like checking the battery charge level and screen brightness so I ended up following the Ubuntu ACPI Debugging Document (https://wiki.ubuntu.com/DebuggingACPI) trying to pinpoint the problem. In the end I was not able to pinpoint the problem, but I discovered that in my case the pnpacpi=off boot option instead of the acpi=off option provided a reasonable solution. With the pnpacpi=off option critical functions like battery charge level monitoring and screen brightness contol works without causing unresponsive GUI.

I am not sure to which package file, what seems to be an ACPI bug. When the pnpacpi=off or acpi=off option is not used, one can observe a very high number of interrupts produced by ACPI in /proc/interrupts crippling GUI responsiveness. I did some testing with Lucid and Maverick Live CDs to determine that the problem occurs in clean Lucid and Maverick installs on Lenovo Ideapad U150, but the impact is more noticable in Lucid.