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| <h1 align="CENTER">Module mod_mmap_static</h1> |
| |
| <p>This module provides mmap()ing of a statically configured |
| list of frequently requested but not changed files.</p> |
| |
| <p><a href="module-dict.html#Status" |
| rel="Help"><strong>Status:</strong></a> Experimental<br /> |
| <a href="module-dict.html#SourceFile" |
| rel="Help"><strong>Source File:</strong></a> |
| mod_mmap_static.c<br /> |
| <a href="module-dict.html#ModuleIdentifier" |
| rel="Help"><strong>Module Identifier:</strong></a> |
| mmap_static_module</p> |
| |
| <h2>Summary</h2> |
| |
| <p>This is an <strong>experimental</strong> module and should |
| be used with care. You can easily create a broken site using |
| this module, read this document carefully. |
| <code>mod_mmap_static</code> maps a list of statically |
| configured files (via <code>MMapFile</code> directives in the |
| main server configuration) into memory through the system call |
| <code>mmap()</code>. This system call is available on most |
| modern Unix derivates, but not on all. There are sometimes |
| system-specific limits on the size and number of files that can |
| be mmap()d, experimentation is probably the easiest way to find |
| out.</p> |
| |
| <p>This mmap()ing is done once at server start or restart, |
| only. So whenever one of the mapped files changes on the |
| filesystem you <em>have</em> to restart the server by at least |
| sending it a HUP or USR1 signal (see the <a |
| href="../stopping.html">Stopping and Restarting</a> |
| documentation). To reiterate that point: if the files are |
| modified <em>in place</em> without restarting the server you |
| may end up serving requests that are completely bogus. You |
| should update files by unlinking the old copy and putting a new |
| copy in place. Most tools such as <code>rdist</code> and |
| <code>mv</code> do this. The reason why this modules doesn't |
| take care of changes to the files is that this check would need |
| an extra <code>stat()</code> every time which is a waste and |
| against the intent of I/O reduction.</p> |
| |
| <h2>Directives</h2> |
| |
| <ul> |
| <li><a href="#mmapfile">MMapFile</a></li> |
| </ul> |
| <hr /> |
| |
| <h2><a id="mmapfile" name="mmapfile">MMapFile</a> |
| directive</h2> |
| |
| <p><a href="directive-dict.html#Syntax" |
| rel="Help"><strong>Syntax:</strong></a> MMapFile |
| <em>filename</em> [<em>filename</em>] ...<br /> |
| <a href="directive-dict.html#Default" |
| rel="Help"><strong>Default:</strong></a> <em>None</em><br /> |
| <a href="directive-dict.html#Context" |
| rel="Help"><strong>Context:</strong></a> server-config<br /> |
| <a href="directive-dict.html#Override" |
| rel="Help"><strong>Override:</strong></a> <em>Not |
| applicable</em><br /> |
| <a href="directive-dict.html#Status" |
| rel="Help"><strong>Status:</strong></a> Experimental<br /> |
| <a href="directive-dict.html#Module" |
| rel="Help"><strong>Module:</strong></a> mod_mmap_static<br /> |
| <a href="directive-dict.html#Compatibility" |
| rel="Help"><strong>Compatibility:</strong></a> Only available |
| in Apache 1.3 or later</p> |
| |
| <p>The <code>MMapFile</code> directive maps one or more files |
| (given as whitespace separated arguments) into memory at server |
| startup time. They are automatically unmapped on a server |
| shutdown. When the files have changed on the filesystem at |
| least a HUP or USR1 signal should be send to the server to |
| re-mmap them.</p> |
| |
| <p>Be careful with the <em>filename</em> arguments: They have |
| to literally match the filesystem path Apache's URL-to-filename |
| translation handlers create. We cannot compare inodes or other |
| stuff to match paths through symbolic links <em>etc.</em> |
| because that again would cost extra <code>stat()</code> system |
| calls which is not acceptable. This module may or may not work |
| with filenames rewritten by <code>mod_alias</code> or |
| <code>mod_rewrite</code>... it is an experiment after all.</p> |
| |
| <p>Notice: You cannot use this for speeding up CGI programs or |
| other files which are served by special content handlers. It |
| can only be used for regular files which are usually served by |
| the Apache core content handler.</p> |
| Example: |
| <pre> |
| MMapFile /usr/local/apache/htdocs/index.html |
| |
| </pre> |
| |
| <p><strong>Note</strong>: don't bother asking for a for a |
| <code>MMapDir</code> directive which recursively maps all the |
| files in a directory. Use Unix the way it was meant to be used. |
| For example, see the <a href="core.html#include">Include</a> |
| directive, and consider this command:</p> |
| <pre> |
| find /www/htdocs -type f -print \ |
| | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf |
| |
| </pre> |
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