According to http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=508148, simpleproxy performs poorly when nss_mdns is in use (because of a call to gethostbyaddr()), which is now the default in at least Debian. The attached patch fixes this by changing the call to getnameinfo()
Switch from gethostbyaddr() to getnameinfo()
Patch applied.