We are running an Apache 2.2 server for a very large web site. Over the past few months we have been having some users reporting slow response times, while others (including our resources, both on the internal network and our home networks) do not see any degradation in performance.

After a ton of investigation, we finally found a "Deny from none" statement in our configuration that was causing reverse DNS lookups (which were timing out) that solved the bulk of our issues, but we still have some customers that we are seeing in the Apache logs (using %D in the log format) with request processing times of > 300s for images, css, javascript and other static content.

We've checked all Deny / Allow statements for reoccurrence of "none", as well as all other things we know of that would cause reverse DNS lookups (such as using "REMOTE_HOST" in rewrite rules, using %a instead of %h in our log format configuration) as well as verified that HostnameLookups is set to "Off".

As an aside, we've also validated that reverse DNS lookups for folks having this problem do not time out - so I'm fairly certain DNS is not an issue in this case.

I've run out of ideas. Are there any Apache configuration scenarios that someone can point me to that I might be missing that would cause request times for static content to take so long only for certain users?

Thank you in advance.