benchmarking mod_gnutls vs mod_ssl

[Simon Josefsson]

All,

I've created a wiki page to explain how to benchmark mod_gnutls vs
mod_ssl with apache2 using only official debian packages.

http://trac.gnutls.org/cgi-bin/trac.cgi/wiki/BenchmarkingModGnuTLS

The initial results place mod_gnutls at 50-75% of the performance of
mod_ssl, which was higher than what I would have guessed.  We haven't
done any organized optimizations.

Results from other architectures or operating systems are very welcome.
Just add the output at the end of the page, under a new 'Results from X'
heading.

One interesting behaviour I noticed when running the tests was that with
mod_ssl, the exchanged TCP packets as seen in wireshark were:

-> client hello
<- server hello, certificate, server key exchange, server hello done
-> client key exchange, change cipher spec, encrypted handshake message
<- change cipher spec, encrypted handshake message
...

but with gnutls we have:

-> client hello
<- server hello
<- certificate
<- server key exchange
<- server hello done
->client key exchange, change cipher spec, encrypted handshake message
<- change cipher spec
<- encrypted handshake message

In other words, gnutls sends each TLS packet in a separate TCP packet.
This may have some impact on performance, but it is too early to tell
for sure.

/Simon