Tired of the fact that my N9 had few battery time I decided to “as a developer” investigate my device a little bit. Last time I did that I was still contracted by Nokia and a few days later I had to fly to Helsinki to help fix a Tracker in combination with contactsd bug. I’m btw. no longer working for Nokia since a few months. So this time I can’t fix it for everyone. Lemme write it here instead.
It’s pretty funny what is going on: I installed Battery-Icon at some point. The software is writing periodically to /usr/share/applications/battery-icon.desktop. Having been a developer at Nokia for the metadata subsystem I know that tracker-miner-fs will reindex .desktop files that change. You don’t really need to be a developer to know that: Tracker’s FS miner is, among other things, responsible for keeping up to date a list of known applications.
Because of Battery-Icon, which people are probably installing to monitor their battery, tracker-miner-fs wakes up to update the metadata. That in turn wakes up tracker-store to store the metadata. That in turn wakes up smartsearch which will fetch from Tracker some textual data. All three will consume power periodically because of this .desktop file write trigger. I’m guessing the power consumption is triggering Battery-Icon to update the .desktop file. And circular power consumption was born.
I guess I should file a bug on Battery-Icon and tell its author to update the .desktop file less often. I think he could for example wait ten minutes before doing that write. Or is the user really interested in accurate battery information each and every second? Looks like Battery-Icon is even writing to the file more frequent every hour. Interesting behavior for a tool monitoring battery to do things in a way that influences power consumption significantly.
Btw, while it’s not fixed: devel-su (enable developer mode, install terminal and password for devel-su is rootme) on your N9 and chmod -x /usr/bin/smartsearch, reboot, then uninstall Battery-Icon and your battery will last longer. I know the guys who were or are on the smartsearch team are going to hate me for that advice. Sorry guys.