Its not solving it, but you can run

echo 3 > /proc/sys/vm/drop_caches

to release some of the cache again, without interfering with running processes.

[root@host2 ~]# free -m
total used free shared buff/cache available
Mem: 15958 3308 158 8 12491 2355
Swap: 1023 177 846
[root@host2 ~]# echo 3 > /proc/sys/vm/drop_caches
[root@host2 ~]# free -m
total used free shared buff/cache available
Mem: 15958 3308 2598 10 10051 2751
Swap: 1023 177 846