ng_patch and swap_pager_getswapspace error

[wishmaster]

Hi,

after I have applied ng_patch for setting TTL for outgoing packets with below rules

kldload ng_ipfw 2>/dev/null
kldload ng_patch 2>/dev/null

/usr/sbin/ngctl -f- <<-SEQ
                 mkpeer ipfw: patch 100 in
                 name ipfw:100 ttl_set
                 msg ttl_set: setconfig { count=1 csum_flags=1 ops=[     \
                         { mode=1 value=128 length=1 offset=8 } ] }
SEQ

/sbin/ipfw add 15002 netgraph 100 ip from me to not me recv "*"

I see this error messages in the log-file:

Dec 18 02:36:56 xxx kernel: swap_pager_getswapspace(32): failed
Dec 18 02:37:00 xxx last message repeated 719 times
Dec 18 02:37:00 xxx kernel: swap_pager_getswapspace(24): failed
Dec 18 02:37:00 xxx kernel: swap_pager_getswapspace(32): failed
Dec 18 02:37:00 xxx kernel: swap_pager_getswapspace(24): failed
Dec 18 02:37:00 xxx kernel: swap_pager_getswapspace(32): failed
......
Dec 18 08:14:12 xxx last message repeated 15 times
Dec 18 08:14:42 xxx last message repeated 12 times
Dec 18 08:14:44 xxx kernel: pid 16634 (nginx), uid 80, was killed: out of swap space
Dec 18 08:14:44 xxx kernel: Dec 18 08:14:44 ukrnasos kernel: pid 16634 (nginx), uid 80, was killed: out of swap space
Dec 18 08:14:46 xxx kernel: swap_pager_getswapspace(32): failed
Dec 18 08:15:12 xxx last message repeated 10 times

This server contains VNET'ed jails for www, db, php.

unaeme -a
FreeBSD xxx 11.1-STABLE FreeBSD 11.1-STABLE #0 r325503: Tue Nov  7 13:38:44 EET 2017     wishmaster at xxx:/usr/obj/usr/src/sys/MY  amd64

What is this?