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

[From: Jan Knutar]

> Doesn't the userland carry some sort of process monitoring, killing
> malignant processes ? If not, we should develop something like this
> for MeeGo.

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 ;)

After that, running powertop (oh, oops, removed from the firmware images 
early on) is nice for finding processes that consume too much CPU /in 
idle/. Normal top can only find processes that just eat too much CPU 
alltogether.

If 3G internet connection is active, then it's a good idea to monitor it 
for traffic. If there's traffic moving occasionally (one packet every 
5-10 seconds seems to be enough to keep the power usage high enough to 
die in 6 hours), tcpdump can help find out what kind of traffic is 
moving and to where. Finding out what app is responsible almost needs 
lsof or similar.

Then the driver bugs, wlan can often wedge itself into consuming 
enormous amounts of power, /especially/ when it's /not/ used/active. 
'ifconfig wlan0 down' often helps with the runaway wlan issue.

Personally the most common causes for runaway power consumption is when 
someone tries to bruteforce my ssh password on the phone (which 
excercises the internet connection and also the cpu heavily), and the 
wlan bug.