Web Performance Tuning

Appendix B. Apache Performance Notes

This appendix was written by Dean Gaudet and is used with his permission. The latest version of this page is on the Web at http://www.apache.org/docs/misc/perf-tuning.html.

Introduction

Apache is a general web server that is designed to be correct first and fast second. Even so, its performance is quite satisfactory. Most sites have less than 10Mbits of outgoing bandwidth, which Apache can fill using only a low-end Pentium-based web server. In practice, sites with more bandwidth require more than one machine to fill the bandwidth due to other constraints (such as CGI or database transaction overhead). For these reasons, the development focus has been mostly on correctness and configurability.

Unfortunately, many folks overlook these facts and cite raw performance numbers as if they are some indication of the quality of a web server product. There is a bare minimum performance that is acceptable; beyond that, extra speed only caters to a much smaller segment of the market. But in order to avoid this hurdle to the acceptance of Apache in some markets, effort was put into Apache 1.3 to bring performance up to a point where the difference with other high-end web servers is minimal.

Finally, there are the folks who just plain want to see how fast something can go. The author falls into this category. The rest of this document is dedicated to these folks who want to squeeze every last bit of performance out of Apache’s current model and want to understand ...