Sometimes when installing software, the /tmp folder gets full to it’s size limit. On a system with 8gb of ram this is 4gb default.
I have hardly ever seen swap used, the ram is rarely ever completely filled with xfce desktop. I think the mate task manger might show the /tmp folder instead of swap but with the multiload NG plugin for xfce4, I believe the background lighter green readout for ram shows /tmp use. Correct me if I’m wrong please.
I ended up messing up the antergos install that was having that issue, and ‘solved’ the problem while I was having to reinstall anyways by setting /tmp as it’s own partition when running through cnchi, and I take that preventative measure now.
You probably shouldn’t resize partitions your system while its running (not even sure that’s possible) but I’ve read several variations of answers to this question.