out of memory with plenty of memory

I have a busy server running Percona 5.6.34-79.1-1.xenial on Ubuntu 16.04. It works great, however, every few weeks, mysqld is shot by out-of-memory killer and I’m not able to find out why.

root@master02:~# grep Out /var/log/syslog
Apr 6 13:37:03 master02 kernel: [17420955.874564] Out of memory: Kill process 36138 (mysqld) score 659 or sacrifice child

So it was killed at 13:37:03.

However, just 2 seconds before, it was using around 110 GB RAM (the system has ~160 GB RAM), with some 55 GB free:

root@master02:~# cat /root/logs/free/free-2017-04-06-13:36:01.log
total used free shared buff/cache available
Mem: 165050752 109560372 593508 189240 54896872 54434632
Swap: 0 0 0

root@master02:~# cat /root/logs/free/free-2017-04-06-13:37:01.log
total used free shared buff/cache available
Mem: 165050752 109582416 602704 189624 54865632 54412072
Swap: 0 0 0

root@master02:~# cat /root/logs/free/free-2017-04-06-13:38:01.log
total used free shared buff/cache available
Mem: 165050752 17982728 92226488 189200 54841536 146007904
Swap: 0 0 0

my.cnf has “innodb-buffer-pool-size = 130G” set.