I run a fairly busy webserver. It's pretty standard: Apache with mod_php on FreeBSD 7.1. It connects to a separate MySQL server. It serves lots of static images.
Users have been complaining of slow response times. Today I got very slow load times, then a "could not connect, try again" from my web browser.
Looking at top showed that the server was practically idle! Yet it was refusing any more connections. After a minute or so, it began responding again (though still slowly).
netstat -s includes
161796 listen queue overflows
but I'm not sure that's the problem, since I've increased somaxconn.
I must be hitting some resource limit. What else should I look at to diagnose the problem?