Minecraft allocate more RAM?

I would like to assign more Ram to Minecraft, which I actually already did.

I assigned 2 gigabytes. But if I open the game and press F3, it says that only 512 Mb are assigned.

What else can I do? I've tried everything imaginable.

That stands with my JVM arguments: -Xmx2G -XX: + UnlockExperimentalVMOptions -XX: + UseG1GC -XX: G1NewSizePercent = 20 -XX: G1ReservePercent = 20 -XX: MaxGCPauseMillis = 50 -XX: G1HeapRegionSize = 32M

It has to use 64bit Java.

And how does it do it

Above is already 64bit

So yes I have 64bit version

And the PC has at least 3G?

Yes he has 8G