In release notes in chapter CHAPTER 1. NEW FEATURES AND ENHANCEMENTS, section Highly Scalable Web Server (Undertow), there is a note with link to configuration guide where should be more information available. This link is not exactly the same as is in current version of configuration guide:

This one is in release notes (does not point me to expected section):

../documentation/en/red-hat-jboss-enterprise-application-platform/version-7.0/configuration-guide/#configuring_the_web_server_undertow

This one is in configuration guide which points me to section of Undertow (see text after hash sign):

../documentation/en/red-hat-jboss-enterprise-application-platform/version-7.0/configuration-guide/#configuring_the_web_server