I have a Sony Vaio VPCZ122GX with 4GB RAM,Nvidia Cards. I install ubuntu 11.10 64 bit. I am currently open : 1 Tab Firefox, Virtual Box with 1 WinXP ~700 RAM, 1 terminal top. That's all. But Memory used is 3.5 GB. I think there must be memory leak while I can see in top: Virtualbox ( 2 process: 696MB + 37MB), Firefox 33MB. Can you help me to fix it. I try googling an searching in askubuntu but no luck.