Web Performance Tuning

Improving Performance from the Server Side

Make sure the web server is not doing reverse DNS lookups.

Web servers are often set by default to take the IP address of the client and do a reverse DNS lookup on it (finding the name associated with the IP address) in order to pass the name to the logging facility or to fill in the REMOTE_HOST CGI environment variable. This is time consuming and not necessary, since a log parsing program can do all the lookups when parsing your log file later. You might be tempted to turn off logging altogether, but that would not be wise. You really need those logs to show how much bandwidth you’re using, whether it’s increasing, and lots of other valuable performance information. CGIs can also do the reverse lookup themselves if they need it.

Increase the TCP retransmit timeout.

TCP will assume a segment has been lost if it has not been acknowledged within a certain amount of time, typically 200 milliseconds. For some slow Internet connections, this is not long enough. TCP segments may be arriving safely at the browser, only to be counted as lost by the server, which then retransmits them. Turning up the TCP retransmit timeout will fix this problem, but it will reduce performance for fast but lossy connections, where the reliability is poor even if the speed is good.

Locate near your users.

Internet Protocol data packets must go through a number of forks in the road on the way from the server to the client. Dedicated computers called routers make ...