document
https://www.zabbix.com/documentation/3.4/manual/appendix/items/vm.memory.size_params
内置变量
https://www.zabbix.com/documentation/3.4/manual/appendix/macros/supported_by_location
内存
Platform available used
Linux<3.14 free + buffers + cached total - free
zabbix_get -s 10.0.3.101 -k vm.memory.size[available]
zabbix_get -s 10.0.3.101 -k vm.memory.size[free]