Comment 82 for bug 760131

@z06gal: Thank you for the suggestion, but unfortunately, 2.6.39.1 shows little improvement on this hardware (Toshiba laptop L305-S5937, Core 2 Duo Intel processors, integrated Intel GM45, etc.).

I would add, however, that I am using Kubuntu now, and have the same issue in Ubuntu. Even without compositing in each, the problem is still manifest.

Here is a summary of Powertop using kernel 2.6.37 and Kwin effects:

Wakeups-from-idle per second : 1122.8 interval: 15.0s
no ACPI power usage estimate available

Top causes for wakeups:
  22.6% ( 77.1) [i915] <interrupt>
  19.8% ( 67.5) USB device 5-1 : USB OPTICAL MOUSE (PIXART)
  15.0% ( 51.0) [ehci_hcd:usb2, uhci_hcd:usb5] <interrupt>
   5.9% ( 20.0) knotify4
   5.0% ( 17.0) kworker/0:0
   4.4% ( 15.0) USB device 1-4 : USB2.0-CRW (Generic)
   4.2% ( 14.4) [ehci_hcd:usb1, uhci_hcd:usb6] <interrupt>
   3.4% ( 11.7) [ath9k] <interrupt>
   0.1% ( 0.4)D plasma-desktop
   2.8% ( 9.5) kworker/u:0
   2.8% ( 9.4) [kernel scheduler] Load balancing tick

Now, i915 is the top cause here, though the "Load balancing tick" often tops at different intervals. Disabling desktop effects doesn't change the results much.

So, disabling desktop effects and reverting to the 2.6.34 kernel results in the following:

Wakeups-from-idle per second : 1182.8 interval: 3.0s
no ACPI power usage estimate available

Top causes for wakeups:
  21.1% ( 44.3) [kernel scheduler] Load balancing tick
  10.5% ( 22.0) [ehci_hcd:usb2, uhci_hcd:usb5] <interrupt>
   9.5% ( 20.0) knotify4
   8.7% ( 18.3) USB device 5-1 : USB OPTICAL MOUSE (PIXART)
   8.6% ( 18.0) [ehci_hcd:usb1, uhci_hcd:usb6] <interrupt>
   7.9% ( 16.7) USB device 1-4 : USB2.0-CRW (Generic)
   4.8% ( 10.0) [kernel core] ath_ani_calibrate (ath_ani_calibrate)
   4.6% ( 9.7) [ath9k] <interrupt>
   4.3% ( 9.0) [kernel core] hrtimer_start (tick_sched_timer)
   2.9% ( 6.0) [ahci] <interrupt>
   2.1% ( 4.3) phy0
   1.9% ( 4.0) [kernel core] usb_hcd_poll_rh_status (rh_timer_func)
   1.9% ( 4.0) kwin
   1.3% ( 2.7) [hda_intel] <interrupt>
   1.3% ( 2.7) alsa-sink
   1.3% ( 2.7) threaded-ml
   1.3% ( 2.7) USB device 2-3 : My Passport 070A (Western Digital)

So I found this other bug report about "[kernel scheduler] Load balancing tick" on Core 2 Duo. I wonder, as Mr. Hessel mentioned back in May, could this be a contributing factor?

https://bugs.launchpad.net/debian/+source/linux-2.6/+bug/524281