Using trunk, httpd is having problems sending files using sendfile() on FreeBSD. 2.2.x does not seem to have this problem. If EnableSendfile off is set, it works correctly. I believe the problem is in server/core_filters.c, in send_brigade_blocking. I don't believe the socket is being woken up correctly when the socket is ready for more data.
CC myself on FreeBSD related bugs
The code has changed in this area since that time. As there is not that much details in the report, it is not easy do do/test anything with it. Could someone with FreeBSD give an update using latest 2.4.x or explain what "is having problems" means ?