[maemo-developers] Quality assurance of "stable" software: my battery drained in few hours

[From: Ian Stirling]

Robin Burchell wrote:
> On Sun, Jun 6, 2010 at 2:23 PM, Ian Stirling <maemo-devel at mauve.plus.com> wrote:
>>> It's pretty hard to find out what's eating the battery on N900. First you
>>> have decide that the battery is being consumed too fast. The default charge
>>> meter occasionally realizes it's very wrong, and rapidly readjusts itself,
>>> giving potential misreadings there. bq27200 certainly helps there, though
>>> there's no "production quality" software available to use it yet. Nokia
>>> Energy Profiler still shines with its absence ;)
>> I'm trying to develop something like this.
>> An energy profiler.
>>
>> The ideal would be 'top' - sorted by power use.
>> But this is hard. :)
> 
> You mean, like, powertop? http://en.wikipedia.org/wiki/PowerTOP

No, fairly unlike powertop.

Powertop sorts by wakeups, which is not useless.

Consider a compute intensive task that uses 99.95% of the CPU.
At the same time, you've got a lightweight task that polls some 
descriptor 10 times a second.

This will appear above the application that's really causing most 
battery drain.

Powertops metric - wakeups per second - is arguably for some loads 
better than top, but it can be horribly misleading for a number of reasons.