Are you running a tickless kernel?
I'd guess that the "extra timer interrupt" is the former timer
interrupt, which will cause 1000 wakeups if you're running a 1000hz
kernel. Tickless kernels do not wake up because of that interrupt.

Your CPU has only 1 ms in C3 state - this could be caused by a 1000hz
kernel as well, because it will wake up every ms.

Peter


On Sun, 2007-05-27 at 10:36 +0200, Antoine Caillau wrote:
> Hi,
> 
> Since 1.4 (or may be 1.3, I do not tested) I've a process who wake up
> my CPU a lot. It is called "extra timer interrupt". Can anyone tell me
> what it is ? 
> 
> Thanks a lot for your help.
> 
> Antoine
> 
>      PowerTOP version 1.4       (C) 2007 Intel Corporation
> 
> Cn          Avg residency (5s)  Long term residency avg
> C0 (cpu running)        (19.6%)
> C1                0.0ms ( 0.0%)                   0.0ms
> C2                3.4ms ( 3.7%)                   2.2ms
> C3                1.0ms (76.7%)                   1.0ms
> 
> 
> Wakeups-from-idle per second : 815.9
> Power usage (ACPI estimate) :  11.3 W (5.4 hours left) 
> 
> Top causes for wakeups:
>   95.6% (1166.6)       <interrupt> : extra timer interrupt 
>    1.1% ( 13.8)       <interrupt> : ohci1394, ipw3945 
>    0.7% (  8.8)       <interrupt> : ehci_hcd:usb1, uhci_hcd:usb2 
>    0.3% (  3.4)   <kernel module> : usb_hcd_poll_rh_status
> (rh_timer_func)
>    0.3% (  3.4)             pcscd : do_nanosleep (hrtimer_wakeup)
>    0.2% (  2.8)        powersaved : queue_delayed_work_on
> (delayed_work_timer_fn 
> ) 
> 
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