Software
DJBDNS dnscache tuning
A Patch for dnscache, which solves issues encoutered when
running heavily loaded servers.
Poll/MAX_UDP
Dnscache has some problems with high load, by default it is limited
to 200 concurrent queries ( MAX_UDP in dnscache.c ), raising this limit
increases the poll frequency as well ( this really needs a smarter algorithm ).
Another issue is that dnscache only handles 1 packet each poll,
making dnscache handle all available packets each poll increases
performance considerably. I found a patch which solves this issue
somewhere on the internet, the site which hosted it seems to have vanished.