RPI3 swap experiments ["was killed: out of swap space" with: "v_free_count: 5439, v_inactive_count: 1"]

[Trev]

Mark Millard via freebsd-arm wrote on 08/06/18 03:39:
> [I think the messages produced for OOM kills are misleading for
> the type of context in this message exchange. More bottom-posted.]
[CHOMP]
> The book's description makes the messages produced misleading:
> (copied from someone else's message)
> 
> 	Aug  5 01:34:24 rpi3 kernel: pid 63223 (ld.lld), uid 0, was killed: out of swap space
> 	Aug  5 01:34:26 rpi3 kernel: pid 63360 (c++), uid 0, was killed: out of swap space
> 	Aug  5 01:34:26 rpi3 kernel: pid 846 (ntpd), uid 123, was killed: out of swap space
> 
> "out of swap space" would appear to apply to the 4.4BSD style of swapping but
> not necessarily to more modern FreeBSD's context.
> 
> "Total Active Working Set too large" (with lots of swap left) seems to be what folks
> are running into in these rpi3/rpi2 examples.
> 
> If the messages had indicated such, this message chain would likely have been
> rather different: working out adjustments of the total active working set size.

Indeed - I was running into "out of swap" on an amd64 VM with 512M 
memory and 512M swap (source upgrade from 11.1R to 11.2R) just 
yesterday, so I tried a few experiments which included a swap partition 
of 256M and that produced lost of these "real" out of swap messages that 
are never seen with the RPi3:

Aug  5 17:54:01 sentinel kernel: swap_pager_getswapspace(32): failed
Aug  5 17:54:02 sentinel last message repeated 4 times
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(25): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(20): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(18): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(17): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(18): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(15): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(32): failed
Aug  5 17:54:01 sentinel kernel: swap_pager_getswapspace(32): failed
Aug  5 17:54:02 sentinel last message repeated 4 times
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(25): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(20): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(18): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(17): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(18): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(15): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(32): failed
Aug  5 17:54:01 sentinel kernel: swap_pager_getswapspace(32): failed
Aug  5 17:54:02 sentinel last message repeated 4 times
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(25): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(20): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(18): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(17): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(18): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(15): failed
Aug  5 17:54:03 sentinel kernel: swap_pager_getswapspace(32): failed
...

before finally:

Aug  5 17:55:04 sentinel kernel: pid 81586 (llvm-tblgen), uid 0, was 
killed: out of swap space
Aug  5 17:55:37 sentinel kernel: pid 80923 (llvm-tblgen), uid 0, was 
killed: out of swap space
Aug  5 17:55:44 sentinel kernel: pid 79998 (make), uid 0, was killed: 
out of swap space