What is "swap" memory?

Swap memory or swap space is the on-disk component of the virtual memory system. It is pre-configured as a swap partition or a swap file when Linux is first installed, but can also be added later.

Disk access is very slow compared to memory access. The system runs more slowly if there is excessive swapping, or thrashing, when the system is unable to find enough free memory. In this situation the only solution is to add more RAM.

To see whether swapping, or paging, has become a performance issue:

  1. Click the Resources tab.

  2. The Memory and Swap History graph shows memory and swap use as percentages.