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SubjectWhat is "extra timer interrupt" in powertop output?
Date
After disabling CD-ROM polling the next top-100 winner is "extra timer 
interrupt":

Cn Avg residency P-states (frequencies)
C0 (cpu running) ( 4.2%) 750 Mhz 0.0%
polling 0.0ms ( 0.0%) 500 Mhz 100.0%
C1 0.0ms ( 0.0%)
C2 0.9ms (95.8%)


Wakeups-from-idle per second : 1101.2 interval: 5.0s
Power usage (ACPI estimate): 11.7W (2.2 hours)

Top causes for wakeups:
31.6% ( 8.4) <interrupt> : extra timer interrupt
15.0% ( 4.0) hald-addon-acpi : schedule_timeout (process_timeout)

I assume, this is what is simply called "timer":
{pts/1}:~%> cat /proc/interrupts
CPU0
0: 9060975 XT-PIC-XT timer
1: 18742 XT-PIC-XT i8042
2: 0 XT-PIC-XT cascade
3: 2 XT-PIC-XT
4: 2 XT-PIC-XT
5: 3 XT-PIC-XT
7: 5 XT-PIC-XT irda0
8: 11 XT-PIC-XT rtc0
9: 3376 XT-PIC-XT acpi
10: 2 XT-PIC-XT
11: 239251 XT-PIC-XT ohci_hcd:usb1, yenta, yenta, yenta, ALI
5451, pcmcia0.0
12: 621206 XT-PIC-XT i8042
14: 225993 XT-PIC-XT ide0
15: 315463 XT-PIC-XT ide1
NMI: 0 Non-maskable interrupts
ERR: 0

Any way to find out why there are so many of them? System is using dynamic
ticks:
{pts/1}:~/src/linux-git%> grep NO_HZ /boot/config
CONFIG_NO_HZ=y

TIA

-andrey


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