My system is Ubuntu 13.04 64 bit + Unity and it uses ~600mb with no other processes-apps open and with preload 900mb, just the core system. Is this the expected amount? It seems a bit steep to me but perhaps this is normal behavior.
ps: my pc has 16gb ram
The operating system makes buffers of as much memory as it can find. To find out how much actual memory is used try this script https://github.com/vaslabs/pi-web-agent/blob/master/usr/libexec/pi-web-agent/scripts/memory_information, it removes cache+bufferes from usage calculations
