For a very long time now Posix systems have had failsafes to create swap on-the-fly to avoid topping out failures. Most modern Linux distros have expanded on that now that drives are commonly automounted. If you've ever run a LiveCd on a box that has a swap partition, they are programmed to automatically detect their presence and utilize them. The *Buntus have accommodated a wide range of boxes and users by avoiding declaring a dedicated swap in /etc/fstab allowing the system to manage it.
That is really convenient but it is also wasteful and inefficient. Unless you've already changed it, if you open the "/etc/fstab" file in a text editor you will see whether or not swap is declared. If you've already created a swap partition I recommend declaring it in fstab because leaving it to the system means it will poll constantly to see if there is enough even if you aren't using any.
Here's a good article on it
IN addition some distros like Ubuntu have a setting that controls just how high a priority swap has, called "swappiness". You can view your default setting (likely 60 - the scale is from 0-100, where 100 is swapping all the time and 0 is almost never) with
Most knowledgeable people agree that Desktop systems, especially laptops, should be set to 10 instead of 60 for a nice performance boost (less thrashing)
You can try it temporarily with
sudo sysctl vm.swappiness=10
and make it permanent by changing the value in /etc/sysctl.conf with a text editor (as root)
Setup as dedicated partition permanently assigned in fstab and swappiness set to 10 should be a quite noticeable improvement.