Re: [Powertop] [powertop] ::wiggle() - what does that do?

[Arjan van de Ven <arjan at linux.intel.com>]

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On 3/19/2013 12:57 PM, Ivan Shapovalov wrote:
> On 19 March 2013 12:53:26 Arjan van de Ven wrote:
>> On 3/19/2013 12:51 PM, Ivan Shapovalov wrote:
>>> Hello all,
>>>
>>> I've been wondering on what does the abstract_cpu::wiggle() function does
>>> and why it is needed?.. All the code says is that it is needed to "have a
>>> record of CPU at the start and end of the perf trace".
>>>
>>> I'm asking just because I feel somewhat uncomfortable to have powertop
>>> changing my scaling frequency back and forth each N seconds. :)
>>
>> the reason this exists is that powertop wants to track what frequency the
>> cpu is at for the duration... ... and there's no way to ask for "current",
>> only to get change notifications
>>
>> so wiggle() forces a change... and from then on we know what it's at.
>
> ...And why isn't it possible to keep the value from last notification?

there may not have been one...

> Because time can pass between measurement end and new measurement start?

yep