Small test program using ports/devel/libmill triggers OOM. Original report: https://lists.freebsd.org/pipermail/freebsd-stable/2017-December/088113.html Latest test: https://people.freebsd.org/~pho/stress/log/chain.txt
FreeBSD does OOM killing based on its own criteria for being unable to achieve sufficient free RAM after enough tries to gain more free RAM, even when there is lots of swap space available. (Trying to buildworld with -j4 on 1 GByte 4-core armv7/aarch64 systems tend to have this issue show up when configured with sufficient swap.) The number of tries is configurable via increasing vm.pageout_oom_seq (default 12 last I knew). Such has been sufficient for those small arm systems doing such builds, using figures like 120 or 1024 or even more. But it looks like you are also running out of swap as well: the messages swap_pager_getswapspace(32): failed indicate that. (Some messages mentioning "out of swap" can be misnomers for some contexts, with the lack of free RAM actually driving the messages to show up independent of the swap space available.) Can you do something to monitor your free RAM availability and swap space availability as things progress? It might suggest some sort of leaking resource(s).
(In reply to Mark Millard from comment #1) Sorry, I should have mentioned that this just a reminder for a problem found with a broken test program (which leaks). That is, this is a stress test program.