Tip
(1 - sum by (instance) (node_memory_MemFree_bytes + node_memory_Buffers_bytes + node_memory_Cached_bytes and on (instance) label_replace(kube_node_role{role="master"}, "instance", "$1", "node", "(.+)")) / sum by (instance) (node_memory_MemTotal_bytes and on (instance) label_replace(kube_node_role{role="master"}, "instance", "$1", "node", "(.+)"))) * 100
[!NOTE]