Practical mod_perl

Chapter 7. Identifying Your Performance Problems

You have been assigned to improve the performance of your company’s web service. The hardest thing is to get started. How should you tackle this task? And how do you sort out the insignificant issues and identify those that will make a difference once resolved?

In this chapter, we look at this problem from different angles. Only after you understand the problem should you start looking for solutions. Don’t search for a solution before the problem has been precisely identified, or you’ll end up wasting a lot of time concentrating on trivial issues. Instead, try to identify where you can make the biggest difference in performance.

Note that in this book, we use the term “web service” to mean the whole aggregate that provides the service: the machine, the network, and the software. Don’t confuse this with web services such as SOAP and XML-RPC.

Looking at the Big Picture

To make the user’s web-browsing experience as painless as possible, every effort must be made to wring the last drop of performance from the server. Many factors affect web site usability, but one of the most important is speed. (This applies to any web server, not just Apache.)

How do we measure the speed of a server? Since the user (and not the computer) is the one that interacts with the web site, one good speed measurement is the time that elapses between the moment the user clicks on a link or presses a Submit button, and the time when the resulting page is fully rendered ...