Prior to Android Oreo I could see Memory usage by going to
Memory but this does not exist any more since upgrading to Android O. Is there any way to see this now or has it been removed completely?
Enable Developer Mode (see here), and go to
Developer options >
This answer will only apply when you are a developer, and you have your development PC near.
First make sure that you have USB debugging enabled.
Then on your PC open a shell that can run
adb (of you don't know what this is, then this answer is not for you)
Then in that shell run
This will open a shell to your Android device, within this shell you are running command line applications on your android device.
Now in this adb shell run
top -s rss | head -n 20. This will print out a list of about 20 apps sorted by RAM usage(-ish, its not precise).
If you are able to enable ADB Root in developer options (Again, if you don't know that this is, then it is not for you), then you can see more details:
In the adb shell run
su. This will elevate your access to the kernel.
This will show a lot more info about ram and swap usage.
To show memory usage in android Oreo, first of all make sure enable developer mode in android Oreo
Enable developer mode android Oreo:
Settings > System > About phone > Tap build number 7 times
Now enabled developer options in android 8.0 Oreo.
Go to settings > System > Developer options > Memory > Memory used by apps