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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HEAD>
<TITLE>Apache module mod_mmap_static</TITLE>
</HEAD>
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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><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 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>
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:
<PRE>
find /www/htdocs -type f -print \
| sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf
</PRE>
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