The check-mbufs script is started using a generated event that makes an event called "check-mbufs-timer." It runs every 600 seconds (10 minutes) and fetches the output of "show system buffers." It uses regular expressions to extract the current mbuf allocation and stuffs it in the utility mib with the key "current-mbufs." An SNMP application can monitor it from there.
Read the document check-mbufs