What does swp use?

Question

linux

Launched htop, the swp parameter is 5GB.
Please tell me, is it in real time, is it so busy or is it for some time?
Well, how to determine the process that occupies it?
I'm not very good at Linux. Help me please.
UPD:
Another question: why does my swap fill up if I have free memory? Here in the same htop I see Mem: 25GB/31GB, Swp: 4GB. That is, the memory is still there.
In addition, I have most of the memory allocated for the mysql cache, and, as I understand it, if there is not enough memory, the cache will simply be cleared.

Answer 1

Hello, this is a special disk partition or file into which the operating system moves individual blocks of RAM in the case when there is not enough RAM for applications to work.

Answer 2

in real time, but the swap fills up very slowly.
swapoff -a && swapon -a

Answer 3

And tell me, please, why does my swap fill up if I have free memory?

swappiness

Answer 4

See what took - https://gist.github.com/holly/6c53b06a5fcae36b4edd