mbuf reference? (and missing man page)

[Michael R. Wayne]

Missing man page:
   4.8 releasse - man netstat has a reference to mbuf(9) but man mbuf says:
      No manual entry for mbuf

Real question:
   I'm seeking some additional documentation on the relationship
   between mbufs, mbuf clusters and network memory usage (essentially
   the output of netstat -m).

   Obviously, the number of mbuf clusters is tunable with kern.ipc.nmbclusters.
   The maximum number of mbufs appears to be 4 * that number (or is that 4
   a tunable?)

   Not sure how network memory allocation is chosen (% of base memory
   size as default?) and, does it grow dynamically or should one be
   building a new kernel once, say, 80% of the mb_map is in use?  Or
   simply ignore occasional high mb_map utilization unless requests
   for memorey are delayed/denied?

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