================================================== ================================================== ================================================== ============================
Ever since I started using my Gear 2 Neo with my HTC One M8 phone (using the guide in this forum), I noticed that my watch consumes battery significantly faster than most of the users have been reporting. Even more strangely, sometimes after resetting both the phone and the watch (and I've done this a lot while experimenting and trying to get more stuff working) I had streaks of stellar battery life, well in line with optimistic reports here and elsewhere, but then, after a while, it started deteriorating very quickly.
So I decided it was time to do something about it. I installed Tizen SDK, hooked the watch up and started poking around. The first thing I noticed my watch CPU was, most of the time, sitting on 40%! Well, that doesn't sound right, does it? Then I noticed the log (located under /var/log/dlog_main) was full with messages related to contact synchronisation. It turns out the damn thing synchronises all of my contacts every several seconds. The trouble is I have well over 1500 contacts (that's consolidated from different sources, the number of raw contacts should be well over 3000). So it takes significant time to do this, meaning my watch (and the phone!) are thrashed by these stupid full contact syncs all the time! What's even more striking is the fact it doesn't help when I change it to "favourites only". Apparently, this affects only the contacts displayed on the watch, however, the sync process still takes all of them.
At this point I started poking around Samsung APK files to try and understand what was going on. Apparently, the APK responsible for contact sync is called GOPROVIDERS. Indeed, if you kill it, the thrashing stops, however, other important functions cease working as well. Aside of Contacts vanishing from the Gear, "Find my phone" is gone as well, but, more importantly, notifications stop working. While I could tolerate the first two, the last one was too much to give up.
I started decompiling and analysing sources. Apparently, there is a process running every several seconds that analyses if any changes have been made to the contacts. It uses pretty bizarre logic which seems to be relying on Samsung-specific fields in the contacts. Now, this already sounds suspicious, and, apparently, leads to full sync every several seconds. Obviously, the more contacts you have, the harder you're hit.
An interesting point in all this is that I'm not 100% sure the logic is working properly even on Samsung devices, so it might well be that the same issue is affecting people with high number of contacts using Samsung phones as well. I'd be really interested to see any feedbacks regarding this.
So, long story short, instead of fixing the logic (which is quite difficult in SMALI), I made a simple change which dilutes this logic invocations, right now 1:64. Since then I'm enjoying MUCH improved battery life.
The fixed APK is attached. You're welcome to give it a try at your own risk (you need to enable installation from untrusted sources + reboot and clean dalvik cache).