[Performance] Memory and CPU usage issues on idling

[pistou]

Environment

React Native Environment Info:
System:
OS: Windows 10
CPU: x64 Intel(R) Core(TM) i7-2600K CPU @ 3.40GHz
Memory: 11.62 GB / 15.90 GB
Binaries:
Yarn: 1.12.3 - D:\Program Files (x86)\Yarn\bin\yarn.CMD
npm: 6.1.0 - C:\Program Files\nodejs\npm.CMD

react 16.6.0
react-native 0.57.4

Description

I'm having some weird issues with the memory and CPU usage, especially when the app is idling ("minimized" in background, not killed).
I'm using Android Studio's profiler and here's what I have:

The vertical separator is the moment when I put my app in the background (openning another app like GMail or whatever).

Am I mistaken or the Memory usage should have go down at this point? I'm not sure about this.

What I don't understand is why do I have a peak in CPU usage and power on a regular basis?
Even if it's like 2-6%, it's still more than I would expect, as the App is currently not running?

Any clue on what is going on?

[react-native-bot]

Can you run react-native info and edit your issue to include these results under the Environment section?

If you believe this information is irrelevant to the reported issue, you may write [skip envinfo] under Environment to let us know.

[dulmandakh]

IIRC, Android apps don't release memory when enters background mode. But you can do it voluntarily using AppState events and release some memory.