Lately, I've been experiencing the very unpleasant phenomenon of my almost new S3 completely locking up and stopping responding to input. It's like a very serious lag that has to either be waited out, or the phone needs to be rebooted by force. Whenever this happens, my underlying apps still work, albeit laggily because CPU spikes through the roof but I cannot interact with my phone - it doesn't react to my touches. If I try forcing it, it only wastes more CPU power on, well, nothing. I am 100% certain that my touch screen is ok - it works as intended in all other cases. When it locks up (and it does so for 10 minutes at a time if not more - I hadn't had the patience to wait longer) I can pull out the battery and reboot that way. The curious thing is, however, that once put back in, the battery will have around 10% less charge in it, every time, unless I pull it out in the first 30 seconds of the lag. It's like its CPU spikes so high through the roof it uses up 10% of my battery in next to no time on operations I cannot identify.
I have activated Show CPU Usage as I suspected the CPU might be overtaxed, and have come to the definitive conclusion that every time these lockups happen, a huge blue bar appears in the Show CPU Usage graph. As soon as it goes away, everything is peachy again.
I have looked it up, but could find no answer more detailed than this: https://stackoverflow.com/questions/10829546/how-to-read-the-stock-cpu-usage-data
My question is - what is the blue bar precisely, and how can I find out what's causing it. Mind you, whenever this happens and my CPU is past 100%, none of the apps listed under the bar actually have a usage higher than 2%. This is not app based, this is something in the OS or the underlying hardware that's malfunctioning - my initial guess was that the internal memory got corrupt somehow and is taking too long to read/write, but I'm just speculating.