How can I clear my SWAP?
Solution 1:
Have you tried turning it off and on again?
As funny as it may seem. You can forcefully clear your swap by turning swap off and on again:
sudo swapoff -a
sudo swapon -a
This will mark all swap partitions as unused by swap (then re-marking them used). Note that this will force all swap memory into physical memory - meaning some bad things might happen if you don't have enough physical memory.
If you're using swap up, you might have a memory leak as someone else has suggested.