Perhaps you installed the 32-bit version of Ubuntu. To check, open up a termianl and type
uname -p. That will tell you if you have 32-bit (in which you'll get iX86, where X can be anything) or x86_64, 64-bit. You should have 64-bit. If not, it's time to back up and reinstall. Also, you have 12GB of RAM, which is quite a bit. I think that you should set your swappiness to 3. For information on how to do this, read the first answer here. Now, if you do have 32-bit Ubuntu, change the swappiness after you install 64-bit Ubuntu, as it will benefit you greatly. Use a task management tool like GNOME System Monitor (preinstalled with Ubuntu) to check your processor use. Maybe it's your processor that's slow. P.S. If you have a solid-state drive, set your swappiness to 0. If you have a solid-state drive, you NEVER EVER EVER want to make or use swap on it. If you have an SSD, I suggest deleting that swap right now.