same thing here ubuntu  12. 04 3.2.0-29-generic   x86_64 
kernel rescheduling and i915 are interrupting the hell out of the cpu

 
Power usage (ACPI estimate): 16.9W (0.7 hours) (long term: 9.9W,/1.2h)

Top causes for wakeups:
  58.9% (949.1)   [Rescheduling interrupts] <kernel IPI>
   9.5% (152.7)   [i915] <interrupt>
   6.1% ( 97.9)   swapper/1
   4.9% ( 78.9)   swapper/0
   3.6% ( 57.6)   swapper/3
   3.3% ( 53.5)   swapper/2
   2.5% ( 40.7)   USB device 1-1.2 : Apple Internal Keyboard / Trackpad (Apple Inc.)
   2.4% ( 38.7)   [ehci_hcd:usb1] <interrupt>
   1.0% ( 16.5)   compiz
   0.7% ( 11.8)   [mmc0, b43] <interrupt>
   0.5% (  8.1)   [acpi] <interrupt>
   0.3% (  5.0)   syndaemon
   0.2% (  4.0)   unity-panel-ser
   0.2% (  3.7)   [TLB shootdowns] <kernel IPI>
   0.2% (  2.7)   [ata_piix, uhci_hcd:usb4] <interrupt>
   0.1% (  2.0)   kworker/1:1
   0.1% (  2.0)   indicator-multi
   0.1% (  2.0)   kworker/u:0
   0.1% (  1.2)   Xorg
   0.1% (  1.0)   gvfs-afc-volume
   0.1% (  1.0)   kworker/u:2
   0.1% (  1.0)   watchdog/0
   0.0% (  0.7)   indicator-cpufr
   0.0% (  0.7)   upowerd
   0.0% (  0.5)   kworker/1:0
   0.0% (  0.3)   accounts-daemon
   0.0% (  0.3)   unity-applicati
   0.0% (  0.3)   zeitgeist-datah
   0.0% (  0.3)   gnome-settings-
   0.0% (  0.2)   update-notifier



/proc/interrupts

        CPU0       CPU1       CPU2       CPU3       
  0:         51             0          0          0   IO-APIC-edge      timer
  8:          1              0          0          0   IO-APIC-edge      rtc0
  9:      23200         0         0          0   IO-APIC-fasteoi   acpi
 17:      49638        0         0          0   IO-APIC-fasteoi   mmc0, b43
 19:      36781          0          0          0   IO-APIC-fasteoi   ata_piix, uhci_hcd:usb4
 21:          0          0          0          0   IO-APIC-fasteoi   uhci_hcd:usb3
 22:         61          0          0          0   IO-APIC-fasteoi   ehci_hcd:usb2
 23:     123062         41          0          0   IO-APIC-fasteoi   ehci_hcd:usb1
 40:          0          0          0          0   PCI-MSI-edge      PCIe PME
 41:          0          0          0          0   PCI-MSI-edge      PCIe PME
 42:          0          0          0          0   PCI-MSI-edge      PCIe PME
 43:          0          0          0          0   PCI-MSI-edge      PCIe PME
 44:          0          0          0          0   PCI-MSI-edge      PCIe PME
 45:         22         21          0          0   PCI-MSI-edge      firewire_ohci
 46:         12          0          0          0   PCI-MSI-edge      mei
 47:     331877          0          0          0   PCI-MSI-edge      i915
 48:        334        806          0          0   PCI-MSI-edge      snd_hda_intel
 49:          1          0          0          0   PCI-MSI-edge      eth0-0
 50:          1          0          0          0   PCI-MSI-edge      eth0-1
 51:          1          0          0          0   PCI-MSI-edge      eth0-2
 52:          1          0          0          0   PCI-MSI-edge      eth0-3
 53:          1          0          0          0   PCI-MSI-edge      eth0-4
NMI:         60         52         21         20   Non-maskable interrupts
LOC:     306654     343382     223778     218322   Local timer interrupts
SPU:          0          0          0          0   Spurious interrupts
PMI:         60         52         21         20   Performance monitoring interrupts
IWI:          2          0          0          0   IRQ work interrupts
RES:     697394     816570     211179     193526   Rescheduling interrupts
CAL:        403       1862       1976       2033   Function call interrupts
TLB:       5353      12264       7844       5713   TLB shootdowns
TRM:         12         12         12         12   Thermal event interrupts
THR:          0          0          0          0   Threshold APIC interrupts
MCE:          0          0          0          0   Machine check exceptions
MCP:         10         10         10         10   Machine check polls