Higher wake-up rate when running on battery

[Alessandro Guido]

I can observe a strange behaviour wrt timer wake-ups when looking at powertop:

 - when running on AC, about 8 wake-ups per second.

 - when running on battery, the number of wake-ups grows to about 11 and the
main wake-up producers are:
  23.1% (  3.9)     <kernel core> : hrtimer_start_range_ns (tick_sched_timer)
  19.2% (  3.2)       <interrupt> : acpi


[ These wake-up rates refer to X running KDE4, wi-fi off (by physical switch)
and no usb device connected. ]

Is this a normal behaviour?

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