Updated the introduction to reflect 2.0

    <h3><a id="introduction"

    name="introduction">Introduction</a></h3>

    <p>Apache is a general webserver, which 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 webserver. 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.</p>

    <p>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 webservers is

    minimal.</p>

    <p>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 why it does some things which

    slow it down.</p>

    <p>Note that this is tailored towards Apache 1.3 on Unix. Some

    of it applies to Apache on NT. Apache on NT has not been tuned

    for performance yet; in fact it probably performs very poorly

    because NT performance requires a different programming

    model.</p>

    <p>Apache 2.0 is a general-purpose webserver, designed to

    provide a balance of flexibility, portability, and performance.

    Although it has not been designed specifically to set benchmark

    records, Apache 2.0 is capable of high performance in many

    real-world situations.</p>

    <p>Compared to Apache 1.3, release 2.0 contains many additional

    optimizations to increase throughput and scalability.  Most of

    these improvements are enabled by default.  However, there are

    compile-time and run-time configuration choices that can

    significantly affect performance.  This document describes the

    options that a server administrator can configure to tune the

    performance of an Apache 2.0 installation.  Some of these

    configuration options enable the httpd to better take advantage

    of the capabilities of the hardware and OS, while others allow

    the administrator to trade functionality for speed.</p>

    <hr />

    <h3><a id="hardware" name="hardware">Hardware and Operating

    <ul>

      <li>Run the latest stable release and patchlevel of the

      operating system that you choose.  Many OS suppliers have

      introduced significant performance improvements their

      introduced significant performance improvements to their

      TCP stacks and thread libraries in recent years.</li>

      <li>If your OS supports a sendfile(2) system call, make

      sure you install the release and/or patches needed to