Any performance, benchmark related work should be done after tuning the server for that. GlassFish's default configuration is not necessarily set up for best performance (which is often subjective and no one configuration is good for every use case/requirement). Please see articles by Jeanfrancois Arcand and Scott Oaks about basic tuning of GlassFish.
In the default case, maximum number of the Grizzly worker threads (request processing
threads) is set to 5. That's why there are no more than 5 "httpWorkerThread-<port-id>-<id>" threads. See request-processing element of domain.xml for reference.
GlassFish has the best web-tier performance, you just need some tuning.
http://weblogs.java.net/blog/sdo/archive/2007/12/a_glassfish_tun.html
[Message sent by forum member 'km' (km)]
http://forums.java.net/jive/thread.jspa?messageID=285039