In FreeBSD 11.x it is possible to change the vfs.zfs.arc_max sysctl variable without rebooting, it's even possible to set it to a lower value than it currently has. In such cases ARC in top(1) reflects the change almost instantly, but the previously used ARC memory remains as "Wired" there and doesn't move under "Free". So is this a grand memory leak, or it will be freed eventually, when more memory is needed?