Trying to understand mbuf-related sysctl parameters

[Tom Ivar Helbekkmo <tih%hamartun.priv.no@localhost>]

I'm trying to tune my main amd64 system, which is router, firewall, NFS
server and mail server for my home network, and needs a lot more mbufs
than the default configuration allows.  Oh, and it's also a database
server, and an OpenVPN connection point for three clients.  And it runs
the MooseFS distributed file system.  Hey, it has 8GiB of RAM!  :)

At the moment, I'm seeing quite reasonable behavior with this:

kern.sbmax=4194304
kern.somaxkva=134217728
kern.mbuf.nmbclusters=262144
net.inet.tcp.sendbuf_max=1048576
net.inet.tcp.recvbuf_max=1048576
net.inet.tcp.sendspace=262144
net.inet.tcp.recvspace=262144
net.inet.udp.sendspace=262144
net.inet.udp.recvspace=262144

However, I can't find anything that really tells me what the
relationship between the first five of these is.  Does it make sense to
have sbmax greater than the sum of sendbuf_max and recvbuf_max?  Should
somaxkva rather be nmbclusters * mclbytes (536870912, or four times what
it is now)?

Any pointers to good reading material would be appreciated, too!

-tih
-- 
It doesn't matter how beautiful your theory is, it doesn't matter how smart
you are. If it doesn't agree with experiment, it's wrong.  -Richard Feynman