Android system RAM consumption is constantly very high. Average memory usage is around 77% even after a reboot. According to "System > Developers > Memory" the top looks like this:
- Android OS 1.1 Gb
- System Android 285 Mb
- System interface 157 Mb
- Google Play services 148 Mb
- Xperia Home 106 Mb
- SwiftKey keyboard 87 Mb
- Google 52 Mb
Summarising the above, it costs about 2 Gb.
Tried complete system reset (with restoring from backup) with no luck — still no clue what could cause such a massive memory usage.
This makes it impossible to use some applications. For example, using car navigation application causes the phone to freeze for minutes and serious overheat. And I'am very luck if none will try to call me during driving: both ring application and the navigation app will freeze for long with no change to do anything. Sometimes, the only solution is to hold the power button and wait for long to see the reboot menu.
