While I don't think this is the best solution, it certainly is the
fastest and in trying to find bottlenecks in network related code
I want this out of the way, so that I don't have to think about it.
What this means, for mbuf clusters anyway is:
- one less malloc() to do for every cluster allocation (replaced with
a relatively quick calculation + assignment)
- no more free() in the cluster free case (replaced with empty space) :-)
This can offer a substantial throughput improvement, but it may not for
all cases. Particularly noticable for larger buffer sends/recvs.
See http://people.freebsd.org/~bmilekic/code/measure2.txt for a rough
idea.
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