vm.memory.size[free] and vm.memory.size[available] return same value on AIX.

$ ./zabbix_agentd -t vm.memory.size[available]
vm.memory.size[available] [u|491425792]
$ ./zabbix_agentd -t vm.memory.size[free]
vm.memory.size[free] [u|491425792]

It seems that vm.memory.size[free] include cache size on AIX platform.