tweak

  <H2>Summary</H2>

  <P>

  This is an <STRONG>experimental</STRONG> module and should be used with

  care.  It maps a list of statically configured files (via

  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>. Although this system

  call is not available on every platform, most of the modern Unix derivates

  provide it. At least those ones conforming to the POSIX.4 definition. The

  size of the mapable files usually has to be less then 2GB.  But this is no

  real restriction for documents on a webserver.

  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.  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 intend of I/O reduction.

  is a waste and against the intent of I/O reduction.

  </P>

  <H2>Directives</H2>

  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 etc. because that again would cost extra <CODE>stat()</CODE>

  system calls which is not acceptable.

  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>

  MMapFile /usr/local/apache/htdocs/index.html

  </PRE>

  <P>

  <b>Note</b>: 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:

  <blockquote><pre>

  find /www/htdocs -type f -print | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf

  </pre></blockquote>

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