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I am tracing my Android system in sleep mode (screen off) by using Systrace in Ddms. In systrace's graph, i saw sometime CPU frequency is 0. So, I want to ask, Can CPU frequency is 0?

Toan Tran Van
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  • Did it *start* at zero or *drop* to zero? Generally speaking, systrace records *changes* in frequencies, so if the frequency never changes you might never see an actual value. – fadden Apr 28 '14 at 17:24

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Yes it can, without the CPU being able to truly sleep we would be charging our phones 10 times a day.

Keeping it short, CPU sleeps when it has nothing to do, and wakes up using special hardware mechanisms in different systems (Radio/AlarmManager/Buttons/Etc..)

skoperst
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  • But when Using showfreq tool for android, it shows at least the Minimum frequency set for that Cpu. Do you know that tool? – Toan Tran Van Apr 27 '14 at 07:25
  • I'm not familiar with that tool. What is the output of it? – skoperst Apr 27 '14 at 07:52
  • The cpu when not asleep has a range of frequencies to save power when there is no need for full processing power, so its probably showing it. But I cant be sure. – skoperst Apr 27 '14 at 08:39