docs/manual/mpm.html - httpd - Git at Google

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     <title>Apache Multi-Processing Modules (MPMs)</title>
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     <h1 align="center">Apache Multi-Processing Modules</h1>

     <p>The Apache HTTP Server is designed to be a powerful and
     flexible web server that can work on a very wide variety of
     platforms in a range of different environments. Different
     platforms and different environments often require different
     features, or may have different ways of implementing the same
     feature most efficiently. Apache has always accommodated a wide
     variety of environments through its modular design. This design
     allows the webmaster to choose which features will be included
     in the server by selecting which modules to load either at
     compile-time or at run-time.</p>

     <p>Apache 2.0 extends this modular design to the most basic
     functions of a web server. The server ships with a selection of
     Multi-Processing Modules (MPMs) which are responsible for
     binding to network ports on the machine, accepting requests,
     and dispatching children to handle the requests.</p>

     <p>Extending the modular design to this level of the server
     allows two important benefits:</p>

     <ul>
       <li>Apache can more cleanly and efficiently support a wide
       variety of operating systems. In particular, the Windows
       version of Apache is now much more efficient, since <a
       href="mod/mpm_winnt.html">mpm_winnt</a> can use native
       networking features in place of the POSIX layer used in
       Apache 1.3. This benefit also extends to other operating
       systems that implement specialized MPMs.</li>

       <li>The server can be better customized for the needs of the
       particular site. For example, sites that need a great deal of
       scalability can choose to use a threaded MPM like <a
       href="mod/worker.html">worker</a>, while sites requiring
       stability or compatibility with older software can use a <a
       href="mod/prefork.html">preforking MPM</a>. In addition,
       special features like serving different hosts under different
       userids (<a href="mod/perchild.html">perchild</a>) can be
       provided.</li>
     </ul>

     <p>At the user level, MPMs appear much like other Apache
     modules. The main difference is that one and only one MPM must
     be loaded into the server at any time. The list of available
     MPMs appears on the <a href="mod/">module index page</a>.</p>

     <h2 align="center">Choosing an MPM</h2>

     <p>MPMs must be chosen during configuration, and compiled into
     the server. Compilers are capable of optimizing a lot of
     functions if threads are used, but only if they know that
     threads are being used. Because some MPMs use threads on Unix
     and others don't, Apache will always perform better if the MPM
     is chosen at configuration time and built into Apache.</p>

     <p>To actually choose the desired MPM, use the argument
     --with-mpm= <em>NAME</em> with the ./configure script.
     <em>NAME</em> is the name of the desired MPM.</p>

     <p>Once the server has been compiled, it is possible to
     determine which MPM was chosen by using <code>./httpd
     -l</code>. This command will list every module that is compiled
     into the server, including the MPM.</p>

     <h2 align="center">MPM Defaults</h2>

     <ul>
       <li>BeOS: beos</li>

       <li>OS/2: mpmt_os2</li>

       <li>Unix: prefork</li>

       <li>Windows: winnt</li>
     </ul>
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	<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
	<meta name="generator" content="HTML Tidy, see www.w3.org" />

	<title>Apache Multi-Processing Modules (MPMs)</title>
	</head>
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	<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
	vlink="#000080" alink="#FF0000">
	<!--#include virtual="header.html" -->

	<h1 align="center">Apache Multi-Processing Modules</h1>

	<p>The Apache HTTP Server is designed to be a powerful and
	flexible web server that can work on a very wide variety of
	platforms in a range of different environments. Different
	platforms and different environments often require different
	features, or may have different ways of implementing the same
	feature most efficiently. Apache has always accommodated a wide
	variety of environments through its modular design. This design
	allows the webmaster to choose which features will be included
	in the server by selecting which modules to load either at
	compile-time or at run-time.</p>

	<p>Apache 2.0 extends this modular design to the most basic
	functions of a web server. The server ships with a selection of
	Multi-Processing Modules (MPMs) which are responsible for
	binding to network ports on the machine, accepting requests,
	and dispatching children to handle the requests.</p>

	<p>Extending the modular design to this level of the server
	allows two important benefits:</p>

	<ul>
	<li>Apache can more cleanly and efficiently support a wide
	variety of operating systems. In particular, the Windows
	version of Apache is now much more efficient, since <a
	href="mod/mpm_winnt.html">mpm_winnt</a> can use native
	networking features in place of the POSIX layer used in
	Apache 1.3. This benefit also extends to other operating
	systems that implement specialized MPMs.</li>

	<li>The server can be better customized for the needs of the
	particular site. For example, sites that need a great deal of
	scalability can choose to use a threaded MPM like <a
	href="mod/worker.html">worker</a>, while sites requiring
	stability or compatibility with older software can use a <a
	href="mod/prefork.html">preforking MPM</a>. In addition,
	special features like serving different hosts under different
	userids (<a href="mod/perchild.html">perchild</a>) can be
	provided.</li>
	</ul>

	<p>At the user level, MPMs appear much like other Apache
	modules. The main difference is that one and only one MPM must
	be loaded into the server at any time. The list of available
	MPMs appears on the <a href="mod/">module index page</a>.</p>

	<h2 align="center">Choosing an MPM</h2>

	<p>MPMs must be chosen during configuration, and compiled into
	the server. Compilers are capable of optimizing a lot of
	functions if threads are used, but only if they know that
	threads are being used. Because some MPMs use threads on Unix
	and others don't, Apache will always perform better if the MPM
	is chosen at configuration time and built into Apache.</p>

	<p>To actually choose the desired MPM, use the argument
	--with-mpm= <em>NAME</em> with the ./configure script.
	<em>NAME</em> is the name of the desired MPM.</p>

	<p>Once the server has been compiled, it is possible to
	determine which MPM was chosen by using <code>./httpd
	-l</code>. This command will list every module that is compiled
	into the server, including the MPM.</p>

	<h2 align="center">MPM Defaults</h2>

	<ul>
	<li>BeOS: beos</li>

	<li>OS/2: mpmt_os2</li>

	<li>Unix: prefork</li>

	<li>Windows: winnt</li>
	</ul>
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