When would Linux choose to swap out instead of using the free memory or buff/cache space?
Here is my data on my computer:
$ free total used free shared buff/cache available Mem: 528011992 51967272 43464000 1285108 432580720 472048004 Swap: 30769148 780 30768368
As we can see, I still have 43Gb of free RAM and 432Gb of buff/cache used. Why would Linux decide to use 780Kb of swap in that situation?
I thought I understood memory management in Linux, but I'm at a loss in this situation.
Maybe useful info: I am running several VPS and I'm pretty sure that their memory isn't committed by default (I'm pretty sure because I have one which I set with 32Gb of RAM and on a reboot I don't see that memory used up). Could the reserved 43Gb be in link with that?
Another note: my computer has two CPUs and the RAM uses NUMA, which is something new to me. Although I could imagine that having an impact, 43Gb of free RAM... and the kernel decides to swap...
Also, I read these answers why is some of my swap space being used, when I still have unused RAM? but it did not really help much. I'm pretty sure I understand the basics.