ROS x86_64 memory usage limit ~~1.6G

Hi
I switch 32 bit to 64 bit x86 mikrotik bare metal (no cloud), currently run 6.44.5

I see 16G of ram

but stuck on 1.61G usage, same like on 32Bit

and there are same problems, such 32 bit when reach 1,61G of ram like ocassionaly 5-10 min los of tghrouput and packet los

Is there limit of max memory to use in 64bit

Regards