<p>The single biggest hardware issue affecting webserver
performance is RAM. A webserver should never ever have to swap,
- swapping increases the latency of each request beyond a point
+ as swapping increases the latency of each request beyond a point
that users consider "fast enough". This causes users to hit
stop and reload, further increasing the load. You can, and
should, control the <directive module="mpm_common"
>MaxClients</directive> setting so that your server
- does not spawn so many children it starts swapping.</p>
+ does not spawn so many children it starts swapping. This procedure
+ for doing this is simple: determine the size of your average Apache
+ process, by looking at your process list via a tool such as
+ <code>top</code>, and divide this into your total available memory,
+ leaving some room for other processes.</p>
<p>Beyond that the rest is mundane: get a fast enough CPU, a
fast enough network card, and fast enough disks, where "fast
</directivelist>
</related>
- <section>
+ <section id="dns">
- <title>HostnameLookups</title>
+ <title>HostnameLookups and other DNS considerations</title>
<p>Prior to Apache 1.3, <directive module="core"
>HostnameLookups</directive> defaulted to <code>On</code>.
This adds latency to every request because it requires a
DNS lookup to complete before the request is finished. In
- Apache 1.3 this setting defaults to <code>Off</code>.
- However (1.3 or later), if you use any <code>Allow from domain</code>
- or <code>Deny from domain</code> directives then you will pay for
+ Apache 1.3 this setting defaults to <code>Off</code>. If you need
+ to have addresses in your log files resolved to hostnames, use the
+ <a href="../programs/logresolve.html"><code>logresolve</code></a>
+ program that comes with Apache, on one of the numerous log
+ reporting packages which are available.</p>
+
+ <p>It is recommended that you do this sort of postprocessing of
+ your log files on some machine other than the production web
+ server machine, in order that this activity not adversely affect
+ server performance.</p>
+
+ If you use any <code><directive module="access">Allow</directive>
+ from domain</code> or <code><directive
+ module="access">Deny</directive> from domain</code>
+ directives (i.e., using a hostname, or a domain name, rather than
+ an IP address) then you will pay for
a double reverse DNS lookup (a reverse, followed by a forward
- to make sure that the reverse is not being spoofed). So for the
- highest performance avoid using these directives (it's fine to
- use IP addresses rather than domain names).</p>
+ to make sure that the reverse is not being spoofed). For best
+ performence, therefore, use IP addresses, rather than names, when
+ using these directives, if possible.</p>
<p>Note that it's possible to scope the directives, such as
within a <code><Location /server-status></code> section.
could consider doing the <code>gethostbyname</code> call in the
specific CGIs that need it.</p>
- <p>Similarly, if you need to have hostname information in your
- server logs in order to generate reports of this information,
- you can postprocess your log file with <a
- href="../programs/logresolve.html"><code>logresolve</code></a>,
- so that these lookups can be done without making the client wait.
- It is recommended that you do this postprocessing, and any other
- statistical analysis of the log file, somewhere other than your
- production web server machine, in order that this activity does
- not adversely affect server performance.</p>
-
</section>
- <section>
+ <section id="symlinks">
<title>FollowSymLinks and SymLinksIfOwnerMatch</title>
</section>
- <section>
+ <section id="htacess">
<title>AllowOverride</title>
</section>
- <section>
+ <section id="negotiation">
<title>Negotiation</title>
determined by reading this single file, rather than having to
scan the directory for files.</p>
+ <p>If your site needs content negotiation consider using
+ <code>type-map</code> files, rather than the <code>Options
+ MultiViews</code> directive to accomplish the negotiation. See the
+ <a href="../content-negotiation.html">Content Negotiation</a>
+ documentation for a full discussion of the methods of negotiation,
+ and instructions for creating <code>type-map</code> files.</p>
+
</section>
<section>
</section>
- <section>
+ <section id="process">
<title>Process Creation</title>
</section>
+ <section id="modules">
+
+ <title>Modules</title>
+
+ <p>Since memory usage is such an important consideration in
+ performance, you should attempt to eliminate modules that youare
+ not actually using. If you have built the modules as <a
+ href="../dso.html">DSOs</a>, eliminating modules is a simple
+ matter of commenting out the associated <directive
+ module="so">LoadModule</directive> directive for that module.
+ This allows you to experiment with removing modules, and seeing
+ if your site still functions in their absense.</p>
+
+ <p>If, on the other hand, you have modules statically linked
+ into your Apache binary, you will need to recompile Apache in
+ order to remove unwanted modules.</p>
+
+ <p>An associated question that arises here is, of course, what
+ modules you need, and which ones you don't. The answer here
+ will, of course, vary from one web site to another. However, the
+ <i>minimal</i> list of modules which you can get by with tends
+ to include <module>mod_mime</module>, <module>mod_dir</module>,
+ and <module>mod_log_config</module>. <code>mod_log_config</code> is,
+ of course, optional, as you can run a web site without log
+ files. This is, however, not recommended.</p>
+
+ </section>
+
<section>
<title>Atomic Operations</title>
projects / apache / commitdiff