I got an alert from the host of my VPS saying I'd run out of memory and they had to restart the thing, and advising me to do stuff. The problem is, the information articles they sent me to tell me how to find out what's happening on my VPS but not how to interpret the numbers. And looking back at the past 30 days of daily snapshots of all those funny numbers,. One of the consistent facts is that my memory used is about 10% of the memory available.
So I'm going to assume some kind of glitch and do nothing.