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ae4298616f
my best guess at what the documentation for the AcceptMutex directive should look like. git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@89533 13f79535-47bb-0310-9956-ffa450edef68
229 lines
7.8 KiB
HTML
229 lines
7.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<TITLE>Apache MPM prefork</TITLE>
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</HEAD>
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<!-- Background white, links blue (unvisited), navy (visited), red (active) -->
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<BODY
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#000080"
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ALINK="#FF0000"
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>
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<!--#include virtual="header.html" -->
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<H1 ALIGN="CENTER">Multi-Processing Module prefork</H1>
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<P>
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This Multi-Processing Module implements a non-threaded, pre-forking
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web server.
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</P>
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<P><A
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HREF="module-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> MPM
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<BR>
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<A
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HREF="module-dict.html#SourceFile"
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REL="Help"
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><STRONG>Source File:</STRONG></A> prefork.c
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<BR>
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<A
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HREF="module-dict.html#ModuleIdentifier"
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REL="Help"
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><STRONG>Module Identifier:</STRONG></A> mpm_prefork_module
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</P>
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<H2>Summary</H2>
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<p>This Multi-Processing Module (MPM) implements a non-threaded,
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pre-forking web server which handles request in a manner very similar
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to the default behavior of Apache 1.3 on Unix.</p>
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<p>A single control process is responsible for launching child
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processes which listen for connections and serve them when they
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arrive. Apache always tries to maintain several <em>spare</em> or
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idle server processes, which stand ready to serve incoming requests.
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In this way, clients do not need to wait for a new child processes to
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be forked before their requests can be served.</p>
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<p>The <code>StartServers</code>, <code>MinSpareServers</code>,
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<code>MaxSpareServers</code>, and <code>MaxServers</code> regulate how
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the parent process creates children to serve requests. In general,
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Apache is very self-regulating, so most sites do not need to adjust
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these directives from their default values. Sites which need to serve
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more than 256 simultaneous requests may need to increase
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<code>MaxClients</code>, while sites with limited memory may need to
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decrease <code>MaxClients</code> to keep the server from thrashing
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(swapping memory to disk and back). More information about tuning
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process creation is provided in the <a
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href="../misc/perf-tuning.html">performance hints</a> documentation.</p>
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<p>While the parent process is usually started as root under Unix
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in order to bind to port 80, the child processes are launched
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by Apache as a less-privileged user. The <code>User</code> and
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<code>Group</code> directives are used to set the privileges
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of the Apache child processes. The child processes must
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be able to read all the content that will be served, but
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should have as few privileges beyond that as possible.
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In addition, unless <a href="../suexec.html">suexec</a> is used,
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these directives also set the privileges which will be inherited
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by CGI scripts.</p>
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<p><code>MaxRequestsPerChild</code> controls how frequently the server
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recycles processes by killing old ones and launching new ones.</p>
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<p>See also: <a href="../bind.html">Setting which addresses and ports
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Apache uses</a>.</p>
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<H2>Directives</H2>
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<UL>
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<li><a href="#acceptmutex">AcceptMutex</a>
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<li><a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>
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<li><a href="mpm_common.html#group">Group</a></li>
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<li><a href="mpm_common.html#pidfile">PidFile</a></li>
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<li><a href="mpm_common.html#listen">Listen</a></li>
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<li><a href="mpm_common.html#listenbacklog">ListenBacklog</a></li>
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<li><a href="mpm_common.html#lockfile">LockFile</a></li>
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<li><a href="mpm_common.html#maxclients">MaxClients</a></li>
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<li><a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li>
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<li><a href="#maxspareservers">MaxSpareServers</a></li>
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<li><a href="#minspareservers">MinSpareServers</a></li>
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<li><a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>
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<li><a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li>
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<li><a href="mpm_common.html#startservers">StartServers</a></li>
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<li><a href="mpm_common.html#user">User</a></li>
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</UL>
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<p><hr>
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<H2><A NAME="AcceptMutex">AcceptMutex Directive</A></H2>
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<p><A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> AcceptMutex default|<EM>method</EM><BR>
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<A
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HREF="directive-dict.html#Default"
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REL="Help"
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><STRONG>Default:</STRONG></A> <code>AcceptMutex default</code><BR>
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<A
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HREF="directive-dict.html#Context"
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REL="Help"
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><STRONG>Context:</STRONG></A> server config<BR>
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<A
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HREF="directive-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> core</p>
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<p>The <code>AcceptMutex</code> directives sets the method that Apache
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uses to serialize multiple children accepting requests on network
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sockets. Prior to Apache 2.0, the method was selectable only at
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compile time. The optimal method to use is highly architecture and
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platform dependent. For further details, see the <a
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href="../misc/perf-tuning.html">performance tuning</a>
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documentation.</p>
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<p>If this directive is set to <code>default</code>, then the
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compile-time selected default will be used. Other possible
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methods are listed below. Note that not all methods are available
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on all platforms. If a method is specified which is not available,
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a message will be written to the error log listing the available
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methods.</p>
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<dl>
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<dt><code>flock</code></dt>
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<dd>uses the <code>flock(2)</code> system call to lock the
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file defined by the <a href="mpm_common.html#lockfile">LockFile</a>
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directive.</dd>
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<dt><code>fcntl</code></dt>
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<dd>uses the <code>fnctl(2)</code> system call to lock the
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file defined by the <a href="mpm_common.html#lockfile">LockFile</a>
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directive.</dd>
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<dt><code>sysvsem</code></dt>
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<dd>uses SySV-style semaphores to implement the mutex.</dd>
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<dt><code>proc_pthread</code></dt>
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<dd>uses POSIX mutexes as implemented by the POSIX Threads (PThreads)
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specification.</dd>
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</dl>
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<hr>
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<H2><A NAME="maxspareservers">MaxSpareServers directive</A></H2>
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<!--%plaintext <?INDEX {\tt MaxSpareServers} directive> -->
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<A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> MaxSpareServers <EM>number</EM><BR>
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<A
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HREF="directive-dict.html#Default"
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REL="Help"
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><STRONG>Default:</STRONG></A> <CODE>MaxSpareServers 10</CODE><BR>
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<A
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HREF="directive-dict.html#Context"
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REL="Help"
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><STRONG>Context:</STRONG></A> server config<BR>
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<A
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HREF="directive-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> core<P>
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The MaxSpareServers directive sets the desired maximum number of <EM>idle</EM>
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child server processes. An idle process is one which is not handling
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a request. If there are more than MaxSpareServers idle, then the parent
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process will kill off the excess processes.<P>
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Tuning of this parameter should only be necessary on very busy sites.
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Setting this parameter to a large number is almost always a bad idea.<P>
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<P>
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See also <A HREF="#minspareservers">MinSpareServers</A> and
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<A HREF="mpm_common.html#startservers">StartServers</A>.<P><HR>
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<H2><A NAME="minspareservers">MinSpareServers directive</A></H2>
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<!--%plaintext <?INDEX {\tt MinSpareServers} directive> -->
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<A
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HREF="directive-dict.html#Syntax"
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REL="Help"
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><STRONG>Syntax:</STRONG></A> MinSpareServers <EM>number</EM><BR>
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<A
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HREF="directive-dict.html#Default"
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REL="Help"
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><STRONG>Default:</STRONG></A> <CODE>MinSpareServers 5</CODE><BR>
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<A
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HREF="directive-dict.html#Context"
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REL="Help"
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><STRONG>Context:</STRONG></A> server config<BR>
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<A
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HREF="directive-dict.html#Status"
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REL="Help"
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><STRONG>Status:</STRONG></A> core<P>
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The MinSpareServers directive sets the desired minimum number of <EM>idle</EM>
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child server processes. An idle process is one which is not handling
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a request. If there are fewer than MinSpareServers idle, then the parent
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process creates new children at a maximum rate of 1 per second.<P>
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Tuning of this parameter should only be necessary on very busy sites.
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Setting this parameter to a large number is almost always a bad idea.<P>
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This directive has no effect on Microsoft Windows.
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<P>
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See also <A HREF="#maxspareservers">MaxSpareServers</A> and
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<A HREF="mpm_common.html#startservers">StartServers</A>.
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<!--#include virtual="footer.html" -->
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</BODY>
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</HTML>
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