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+<p class="apache">Apache HTTP Server Version 2.4</p>
+<img alt="" src="../images/feather.png" /></div>
+<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
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+<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.4</a> &gt; <a href="./">Modules</a></div>
+<div id="page-content">
+<div id="preamble"><h1>Apache MPM Common Directives</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
+<a href="../en/mod/mpm_common.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../fr/mod/mpm_common.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
+<a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
+</div>
+<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A collection of directives that are implemented by
+more than one multi-processing module (MPM)</td></tr>
+<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr></table>
+</div>
+<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3 class="directives">Directives</h3>
+<ul id="toc">
+<li><img alt="" src="../images/down.gif" /> <a href="#coredumpdirectory">CoreDumpDirectory</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#enableexceptionhook">EnableExceptionHook</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#gracefulshutdowntimeout">GracefulShutdownTimeout</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#listen">Listen</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#listenbacklog">ListenBackLog</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#listencoresbucketsratio">ListenCoresBucketsRatio</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#maxconnectionsperchild">MaxConnectionsPerChild</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#maxmemfree">MaxMemFree</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#maxrequestworkers">MaxRequestWorkers</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#maxsparethreads">MaxSpareThreads</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#minsparethreads">MinSpareThreads</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#pidfile">PidFile</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#receivebuffersize">ReceiveBufferSize</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#scoreboardfile">ScoreBoardFile</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#sendbuffersize">SendBufferSize</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#serverlimit">ServerLimit</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#startservers">StartServers</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#startthreads">StartThreads</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#threadlimit">ThreadLimit</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#threadsperchild">ThreadsPerChild</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#threadstacksize">ThreadStackSize</a></li>
+</ul>
+<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mpm_common">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mpm_common">Report a bug</a></li></ul><h3>See also</h3>
+<ul class="seealso">
+<li><a href="#comments_section">Comments</a></li></ul></div>
+
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="CoreDumpDirectory" id="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory" id="coredumpdirectory">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory where Apache HTTP Server attempts to
+switch before dumping core</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CoreDumpDirectory <var>directory</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for the default setting</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr>
+</table>
+ <p>This controls the directory to which Apache httpd attempts to
+ switch before dumping core. If your operating system is configured to
+ create core files in the working directory of the crashing process,
+ <code class="directive">CoreDumpDirectory</code> is necessary to change working
+ directory from the default <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>
+ directory, which should not be writable by the user the server runs as.</p>
+
+ <p>If you want a core dump for debugging, you can use this directive to
+ place it in a different location. This directive has no effect if your
+ operating system is not configured to write core files to the working directory
+ of the crashing processes.</p>
+
+ <div class="warning">
+ <h3>Security note for Linux systems</h3>
+
+ <p>Using this directive on Linux may allow other processes on
+ the system (if running with similar privileges, such as CGI
+ scripts) to attach to httpd children via the <code>ptrace</code>
+ system call. This may make weaken the protection from certain
+ security attacks. It is not recommended to use this directive
+ on production systems.</p>
+ </div>
+
+ <div class="note"><h3>Core Dumps on Linux</h3>
+ <p>If Apache httpd starts as root and switches to another user, the
+ Linux kernel <em>disables</em> core dumps even if the directory is
+ writable for the process. Apache httpd (2.0.46 and later) reenables core dumps
+ on Linux 2.4 and beyond, but only if you explicitly configure a <code class="directive">CoreDumpDirectory</code>.</p>
+ </div>
+
+ <div class="note">
+ <h3>Core Dumps on BSD</h3>
+ <p>To enable core-dumping of suid-executables on BSD-systems (such
+ as FreeBSD), set <code>kern.sugid_coredump</code> to 1.
+ </p>
+ </div>
+
+ <div class="note"><h3>Specific signals</h3>
+ <p><code class="directive">CoreDumpDirectory</code> processing only occurs for
+ a select set of fatal signals: SIGFPE, SIGILL, SIGABORT,
+ SIGSEGV, and SIGBUS.</p>
+ <p>On some operating systems, SIGQUIT also results in a core dump but
+ does not go through <code class="directive">CoreDumpDirectory</code> or
+ <code class="directive">EnableExceptionHook</code> processing, so the core
+ location is dictated entirely by the operating system.</p>
+ </div>
+
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="EnableExceptionHook" id="EnableExceptionHook">EnableExceptionHook</a> <a name="enableexceptionhook" id="enableexceptionhook">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a hook that runs exception handlers
+after a crash</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableExceptionHook On|Off</code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableExceptionHook Off</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr>
+</table>
+ <p>For safety reasons this directive is only available if the server was
+ configured with the <code>--enable-exception-hook</code> option. It
+ enables a hook that allows external modules to plug in and do something
+ after a child crashed.</p>
+
+ <p>There are already two modules, <code>mod_whatkilledus</code> and
+ <code>mod_backtrace</code> that make use of this hook. Please have a
+ look at Jeff Trawick's <a href="https://emptyhammock.com/projects/httpd/diag/">EnableExceptionHook site</a> for more information about these.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="GracefulShutdownTimeout" id="GracefulShutdownTimeout">GracefulShutdownTimeout</a> <a name="gracefulshutdowntimeout" id="gracefulshutdowntimeout">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a timeout after which a gracefully shutdown server
+will exit.</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>GracefulShutdownTimeout <var>seconds</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>GracefulShutdownTimeout 0</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.2 and later</td></tr>
+</table>
+ <p>The <code class="directive">GracefulShutdownTimeout</code> specifies
+ how many seconds after receiving a "graceful-stop" signal, a
+ server should continue to run, handling the existing connections.</p>
+
+ <p>Setting this value to zero means that the server will wait
+ indefinitely until all remaining requests have been fully served.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="Listen" id="Listen">Listen</a> <a name="listen" id="listen">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>IP addresses and ports that the server
+listens to</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Listen [<var>IP-address</var>:]<var>portnumber</var> [<var>protocol</var>]</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The <var>protocol</var> argument was added in 2.1.5</td></tr>
+</table>
+ <p>The <code class="directive">Listen</code> directive instructs Apache httpd to
+ listen to only specific IP addresses or ports; by default it
+ responds to requests on all IP interfaces. <code class="directive">Listen</code>
+ is now a required directive. If it is not in the config file, the
+ server will fail to start. This is a change from previous versions
+ of Apache httpd.</p>
+
+ <p>The <code class="directive">Listen</code> directive tells the server to
+ accept incoming requests on the specified port or address-and-port
+ combination. If only a port number is specified, the server listens to
+ the given port on all interfaces. If an IP address is given as well
+ as a port, the server will listen on the given port and
+ interface.</p>
+
+ <p>Multiple <code class="directive">Listen</code> directives may be used to
+ specify a number of addresses and ports to listen to. The server will
+ respond to requests from any of the listed addresses and ports.</p>
+
+ <p>For example, to make the server accept connections on both
+ port 80 and port 8000, use:</p>
+
+ <pre class="prettyprint lang-config">Listen 80
+Listen 8000</pre>
+
+
+ <p>To make the server accept connections on two specified
+ interfaces and port numbers, use </p>
+
+ <pre class="prettyprint lang-config">Listen 192.170.2.1:80
+Listen 192.170.2.5:8000</pre>
+
+
+ <p>IPv6 addresses must be surrounded in square brackets, as in the
+ following example:</p>
+
+ <pre class="prettyprint lang-config">Listen [2001:db8::a00:20ff:fea7:ccea]:80</pre>
+
+
+ <p>The optional <var>protocol</var> argument is not required for most
+ configurations. If not specified, <code>https</code> is the default for
+ port 443 and <code>http</code> the default for all other ports. The
+ protocol is used to determine which module should handle a request, and
+ to apply protocol specific optimizations with the
+ <code class="directive"><a href="../mod/core.html#acceptfilter">AcceptFilter</a></code> directive.</p>
+
+ <p>You only need to set the protocol if you are running on non-standard
+ ports. For example, running an <code>https</code> site on port 8443:</p>
+
+ <pre class="prettyprint lang-config">Listen 192.170.2.1:8443 https</pre>
+
+
+ <div class="note"><h3>Error condition</h3>
+ Multiple <code class="directive">Listen</code> directives for the same ip
+ address and port will result in an <code>Address already in use</code>
+ error message.
+ </div>
+
+
+<h3>See also</h3>
+<ul>
+<li><a href="../dns-caveats.html">DNS Issues</a></li>
+<li><a href="../bind.html">Setting which addresses and ports Apache HTTP Server
+ uses</a></li>
+<li><a href="http://wiki.apache.org/httpd/CouldNotBindToAddress">Further
+discussion of the <code>Address already in use</code> error message,
+including other causes.</a></li>
+</ul>
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ListenBackLog" id="ListenBackLog">ListenBackLog</a> <a name="listenbacklog" id="listenbacklog">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum length of the queue of pending connections</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenBackLog <var>backlog</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenBackLog 511</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+</table>
+ <p>The maximum length of the queue of pending connections.
+ Generally no tuning is needed or desired; however on some
+ systems, it is desirable to increase this when under a TCP SYN
+ flood attack. See the backlog parameter to the
+ <code>listen(2)</code> system call.</p>
+
+ <p>This will often be limited to a smaller number by the
+ operating system. This varies from OS to OS. Also note that
+ many OSes do not use exactly what is specified as the backlog,
+ but use a number based on (but normally larger than) what is
+ set.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ListenCoresBucketsRatio" id="ListenCoresBucketsRatio">ListenCoresBucketsRatio</a> <a name="listencoresbucketsratio" id="listencoresbucketsratio">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Ratio between the number of CPU cores (online) and the number of
+listeners' buckets</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenCoresBucketsRatio <var>ratio</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenCoresBucketsRatio 0 (disabled)</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.4.17, with a kernel supporting
+the socket option <code>SO_REUSEPORT</code> and distributing new connections
+evenly across listening processes' (or threads') sockets using it (eg. Linux
+3.9 and later, but not the current implementations of <code>SO_REUSEPORT</code>
+in *BSDs.</td></tr>
+</table>
+ <p>A <var>ratio</var> between the number of (online) CPU cores and the
+ number of listeners' buckets can be used to make Apache HTTP Server create
+ <code>num_cpu_cores / ratio</code> listening buckets, each containing its
+ own <code class="directive"><a href="#listen">Listen</a></code>-ing socket(s) on the same port(s), and
+ then make each child handle a single bucket (with round-robin distribution
+ of the buckets at children creation time).</p>
+
+ <div class="note"><h3>Meaning of "online" CPU core</h3>
+ <p>On Linux (and also BSD) a CPU core can be turned on/off if
+ <a href="https://www.kernel.org/doc/Documentation/cpu-hotplug.txt">Hotplug</a>
+ is configured, therefore <code class="directive">ListenCoresBucketsRatio</code> needs to
+ take this parameter into account while calculating the number of buckets to create.</p>
+ </div>
+
+ <p><code class="directive">ListenCoresBucketsRatio</code> can improve the
+ scalability when accepting new connections is/becomes the bottleneck.
+ On systems with a large number of CPU cores, enabling this feature has
+ been tested to show significant performances improvement and shorter
+ responses time.</p>
+
+ <p>There must be at least twice the number of CPU cores than the
+ configured <var>ratio</var> for this to be active. The recommended
+ <var>ratio</var> is <code>8</code>, hence at least <code>16</code>
+ cores should be available at runtime when this value is used.
+ The right <var>ratio</var> to obtain maximum performance needs to be calculated
+ for each target system, testing multiple values and observing the variations in your
+ key performance metrics.</p>
+
+ <p>This directive influences the calculation of the
+ <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code> and
+ <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code> lower bound values.
+ The number of children processes needs to be a multiple of the number
+ of buckets to optimally accept connections.</p>
+
+ <div class="note">
+ <h3>Multiple <code class="directive">Listen</code>ers or Apache HTTP servers on
+ the same IP address and port</h3>
+ <p>Setting the <code>SO_REUSEPORT</code> option on the listening socket(s)
+ consequently allows multiple processes (sharing the same <code>EUID</code>,
+ e.g. <code>root</code>) to bind to the the same IP address and port,
+ without the binding error raised by the system in the usual case.</p>
+ <p>This also means that multiple instances of Apache httpd configured on a
+ same <code>IP:port</code> and with a positive <code class="directive">ListenCoresBucketsRatio</code>
+ would start without an error too, and then run with incoming connections
+ evenly distributed across both instances (this is NOT a recommendation or
+ a sensible usage in any case, but just a notice that it would prevent such
+ possible issues to be detected).</p>
+ <p>Within the same instance, Apache httpd will check and fail to start if
+ multiple <code class="directive">Listen</code> directives on the exact same IP (or
+ hostname) and port are configured, thus avoiding the creation of some
+ duplicated buckets which would be useless and kill performances. However
+ it can't (and won't try harder to) catch all the possible overlapping cases
+ (like a hostname resolving to an IP used elsewhere).</p>
+ </div>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="MaxConnectionsPerChild" id="MaxConnectionsPerChild">MaxConnectionsPerChild</a> <a name="maxconnectionsperchild" id="maxconnectionsperchild">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on the number of connections that an individual child server
+will handle during its life</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxConnectionsPerChild <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxConnectionsPerChild 0</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available Apache HTTP Server 2.3.9 and later. The old name
+<code>MaxRequestsPerChild</code> is still supported.</td></tr>
+</table>
+ <p>The <code class="directive">MaxConnectionsPerChild</code> directive sets
+ the limit on the number of connections that an individual child
+ server process will handle. After
+ <code class="directive">MaxConnectionsPerChild</code> connections, the child
+ process will die. If <code class="directive">MaxConnectionsPerChild</code> is
+ <code>0</code>, then the process will never expire.</p>
+
+ <p>Setting <code class="directive">MaxConnectionsPerChild</code> to a
+ non-zero value limits the amount of memory that a process can consume
+ by (accidental) memory leakage.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="MaxMemFree" id="MaxMemFree">MaxMemFree</a> <a name="maxmemfree" id="maxmemfree">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of memory that the main allocator is allowed
+to hold without calling <code>free()</code></td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxMemFree <var>KBytes</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxMemFree 2048</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code></td></tr>
+</table>
+ <p>The <code class="directive">MaxMemFree</code> directive sets the
+ maximum number of free Kbytes that every allocator is allowed
+ to hold without calling <code>free()</code>. In threaded MPMs, every
+ thread has its own allocator. When set
+ to zero, the threshold will be set to unlimited.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="MaxRequestWorkers" id="MaxRequestWorkers">MaxRequestWorkers</a> <a name="maxrequestworkers" id="maxrequestworkers">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of connections that will be processed
+simultaneously</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRequestWorkers <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr>
+</table>
+ <p>The <code class="directive">MaxRequestWorkers</code> directive sets the limit
+ on the number of simultaneous requests that will be served. Any
+ connection attempts over the <code class="directive">MaxRequestWorkers</code>
+ limit will normally be queued, up to a number based on the
+ <code class="directive"><a href="#listenbacklog">ListenBacklog</a></code>
+ directive. Once a child process is freed at the end of a different
+ request, the connection will then be serviced.</p>
+
+ <p>For non-threaded servers (<em>i.e.</em>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>),
+ <code class="directive">MaxRequestWorkers</code> translates into the maximum
+ number of child processes that will be launched to serve requests.
+ The default value is <code>256</code>; to increase it, you must also raise
+ <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
+
+ <p>For threaded and hybrid servers (<em>e.g.</em> <code class="module"><a href="../mod/event.html">event</a></code>
+ or <code class="module"><a href="../mod/worker.html">worker</a></code>), <code class="directive">MaxRequestWorkers</code> restricts
+ the total number of threads that will be available to serve clients.
+ For hybrid MPMs, the default value is <code>16</code> (<code class="directive"><a href="#serverlimit">ServerLimit</a></code>) multiplied by the value of
+ <code>25</code> (<code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>). Therefore, to increase <code class="directive">MaxRequestWorkers</code> to a value that requires more than 16 processes,
+ you must also raise <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
+
+ <p><code class="directive">MaxRequestWorkers</code> was called
+ <code class="directive">MaxClients</code> before version 2.3.13. The old name is still
+ supported.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="MaxSpareThreads" id="MaxSpareThreads">MaxSpareThreads</a> <a name="maxsparethreads" id="maxsparethreads">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle threads</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareThreads <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+</table>
+ <p>Maximum number of idle threads. Different MPMs deal with this
+ directive differently.</p>
+
+ <p>For <code class="module"><a href="../mod/worker.html">worker</a></code> and <code class="module"><a href="../mod/event.html">event</a></code>, the default is
+ <code>MaxSpareThreads 250</code>. These MPMs deal with idle threads
+ on a server-wide basis. If there are too many idle threads in the
+ server, then child processes are killed until the number of idle
+ threads is less than this number. Additional processes/threads
+ might be created if <code class="directive"><a href="#listencoresbucketsratio">ListenCoresBucketsRatio</a></code>
+ is enabled.</p>
+
+ <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
+ <code>MaxSpareThreads 100</code>. Since this MPM runs a
+ single-process, the spare thread count is also server-wide.</p>
+
+ <p><code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> works
+ similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. For
+ <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>10</code>.</p>
+
+ <div class="note"><h3>Restrictions</h3>
+ <p>The range of the <code class="directive">MaxSpareThreads</code> value
+ is restricted. Apache httpd will correct the given value automatically
+ according to the following rules:</p>
+ <ul>
+ <li><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> wants the value to be greater than
+ <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>.</li>
+
+ <li>For <code class="module"><a href="../mod/worker.html">worker</a></code> and <code class="module"><a href="../mod/event.html">event</a></code>, the value
+ must be greater or equal to the sum of <code class="directive"><a href="#minsparethreads">
+ MinSpareThreads</a></code> and <code class="directive"><a href="#threadsperchild">
+ ThreadsPerChild</a></code>.</li>
+ </ul>
+ </div>
+
+<h3>See also</h3>
+<ul>
+<li><code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code></li>
+<li><code class="directive"><a href="#startservers">StartServers</a></code></li>
+<li><code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code></li>
+</ul>
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="MinSpareThreads" id="MinSpareThreads">MinSpareThreads</a> <a name="minsparethreads" id="minsparethreads">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle threads available to handle request
+spikes</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareThreads <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+</table>
+ <p>Minimum number of idle threads to handle request spikes.
+ Different MPMs deal with this directive differently.</p>
+
+ <p><code class="module"><a href="../mod/worker.html">worker</a></code> and <code class="module"><a href="../mod/event.html">event</a></code> use a default of
+ <code>MinSpareThreads 75</code> and deal with idle threads on a server-wide
+ basis. If there aren't enough idle threads in the server, then child
+ processes are created until the number of idle threads is greater
+ than <var>number</var>. Additional processes/threads
+ might be created if <code class="directive"><a href="#listencoresbucketsratio">ListenCoresBucketsRatio</a></code>
+ is enabled.</p>
+
+ <p><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> uses a default of
+ <code>MinSpareThreads 10</code> and, since it is a single-process
+ MPM, tracks this on a server-wide basis.</p>
+
+ <p><code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> works
+ similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. For
+ <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>5</code>.</p>
+
+<h3>See also</h3>
+<ul>
+<li><code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code></li>
+<li><code class="directive"><a href="#startservers">StartServers</a></code></li>
+<li><code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code></li>
+</ul>
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="PidFile" id="PidFile">PidFile</a> <a name="pidfile" id="pidfile">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File where the server records the process ID
+of the daemon</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PidFile <var>filename</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>PidFile logs/httpd.pid</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+</table>
+ <p>The <code class="directive">PidFile</code> directive sets the file to
+ which the server records the process id of the daemon. If the
+ filename is not absolute, then it is assumed to be relative to the
+ <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
+
+ <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">PidFile /var/run/apache.pid</pre>
+</div>
+
+ <p>It is often useful to be able to send the server a signal,
+ so that it closes and then re-opens its <code class="directive"><a href="../mod/core.html#errorlog">ErrorLog</a></code> and <code class="directive"><a href="../mod/mod_log_config.html#transferlog">TransferLog</a></code>, and
+ re-reads its configuration files. This is done by sending a
+ SIGHUP (kill -1) signal to the process id listed in the
+ <code class="directive">PidFile</code>.</p>
+
+ <p>The <code class="directive">PidFile</code> is subject to the same
+ warnings about log file placement and <a href="../misc/security_tips.html#serverroot">security</a>.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>As of Apache HTTP Server 2, we recommended that you only use the <code class="program"><a href="../programs/apachectl.html">apachectl</a></code> script, or the init script that your OS provides,
+ for (re-)starting or stopping the server.</p>
+ </div>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ReceiveBufferSize" id="ReceiveBufferSize">ReceiveBufferSize</a> <a name="receivebuffersize" id="receivebuffersize">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP receive buffer size</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ReceiveBufferSize <var>bytes</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ReceiveBufferSize 0</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+</table>
+ <p>The server will set the TCP receive buffer size to the number of
+ bytes specified.</p>
+
+ <p>If set to the value of <code>0</code>, the server will use the
+ OS default.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ScoreBoardFile" id="ScoreBoardFile">ScoreBoardFile</a> <a name="scoreboardfile" id="scoreboardfile">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the file used to store coordination data for
+the child processes</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScoreBoardFile <var>file-path</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScoreBoardFile logs/apache_runtime_status</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code></td></tr>
+</table>
+ <p>Apache HTTP Server uses a scoreboard to communicate between its parent
+ and child processes. Some architectures require a file to facilitate
+ this communication. If the file is left unspecified, Apache httpd first
+ attempts to create the scoreboard entirely in memory (using anonymous
+ shared memory) and, failing that, will attempt to create the file on
+ disk (using file-based shared memory). Specifying this directive causes
+ Apache httpd to always create the file on the disk.</p>
+
+ <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">ScoreBoardFile /var/run/apache_runtime_status</pre>
+</div>
+
+ <p>File-based shared memory is useful for third-party applications
+ that require direct access to the scoreboard.</p>
+
+ <p>If you use a <code class="directive">ScoreBoardFile</code>, then
+ you may see improved speed by placing it on a RAM disk. But be
+ careful that you heed the same warnings about log file placement
+ and <a href="../misc/security_tips.html">security</a>.</p>
+
+<h3>See also</h3>
+<ul>
+<li><a href="../stopping.html">Stopping and Restarting
+Apache HTTP Server</a></li>
+</ul>
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="SendBufferSize" id="SendBufferSize">SendBufferSize</a> <a name="sendbuffersize" id="sendbuffersize">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP buffer size</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SendBufferSize <var>bytes</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SendBufferSize 0</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+</table>
+ <p>Sets the server's TCP send buffer size to the number of bytes
+ specified. It is often useful to set this past the OS's standard
+ default value on high speed, high latency connections
+ (<em>i.e.</em>, 100ms or so, such as transcontinental fast pipes).</p>
+
+ <p>If set to the value of <code>0</code>, the server will use the
+ default value provided by your OS.</p>
+
+ <p>Further configuration of your operating system may be required to elicit
+ better performance on high speed, high latency connections.</p>
+
+ <div class="note"> <p> On some operating systems, changes in TCP behavior resulting
+ from a larger <code class="directive">SendBufferSize</code> may not be seen unless
+ <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code> is set to OFF. This
+ interaction applies only to static files.</p> </div>
+
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ServerLimit" id="ServerLimit">ServerLimit</a> <a name="serverlimit" id="serverlimit">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Upper limit on configurable number of processes</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerLimit <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr>
+</table>
+ <p>For the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, this directive sets the
+ maximum configured value for <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> for the lifetime of the
+ Apache httpd process. For the <code class="module"><a href="../mod/worker.html">worker</a></code> and <code class="module"><a href="../mod/event.html">event
+ </a></code> MPMs, this directive in combination with <code class="directive"><a href="#threadlimit">ThreadLimit</a></code> sets
+ the maximum configured value for <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> for the lifetime of the
+ Apache httpd process. For the <code class="module"><a href="../mod/event.html">event</a></code> MPM, this directive
+ also defines how many old server processes may keep running and finish processing
+ open connections.
+ Any attempts to change this directive during a restart will be ignored, but
+ <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> can be modified
+ during a restart.</p>
+
+ <p>Special care must be taken when using this directive. If
+ <code class="directive">ServerLimit</code> is set to a value much higher
+ than necessary, extra, unused shared memory will be allocated. If
+ both <code class="directive">ServerLimit</code> and <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> are set to values
+ higher than the system can handle, Apache httpd may not start or the
+ system may become unstable.</p>
+
+ <p>With the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, use this directive only
+ if you need to set <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> higher than 256 (default).
+ Do not set the value of this directive any higher than what you
+ might want to set <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> to.</p>
+
+ <p>With <code class="module"><a href="../mod/worker.html">worker</a></code>, use this directive only if your
+ <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers
+ </a></code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>
+ settings require more than 16 server processes (default). Do not set
+ the value of this directive any higher than the number of server
+ processes required by what you may want for <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers </a></code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</p>
+
+ <p>With <code class="module"><a href="../mod/event.html">event</a></code>, increase this directive if the process
+ number defined by your <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> settings, plus the
+ number of gracefully shutting down processes, is more than 16 server
+ processes (default).</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>There is a hard limit of <code>ServerLimit 20000</code> compiled
+ into the server (for the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM 200000). This is
+ intended to avoid nasty effects caused by typos. To increase it
+ even further past this limit, you will need to modify the value of
+ MAX_SERVER_LIMIT in the mpm source file and rebuild the server.</p>
+ </div>
+
+<h3>See also</h3>
+<ul>
+<li><a href="../stopping.html">Stopping and Restarting Apache HTTP Server</a></li>
+</ul>
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="StartServers" id="StartServers">StartServers</a> <a name="startservers" id="startservers">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of child server processes created at startup</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartServers <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+</table>
+ <p>The <code class="directive">StartServers</code> directive sets the
+ number of child server processes created on startup. As the number
+ of processes is dynamically controlled depending on the load, (see
+ <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>,
+ <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code>,
+ <code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code>)
+ there is usually little reason to adjust this parameter.</p>
+
+ <p>The default value differs from MPM to MPM. <code class="module"><a href="../mod/worker.html">worker</a></code> and
+ <code class="module"><a href="../mod/event.html">event</a></code> default to <code>StartServers 3</code>; <code class="module"><a href="../mod/prefork.html">
+ prefork</a></code> defaults to <code>5</code>; <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code>
+ defaults to <code>2</code>.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="StartThreads" id="StartThreads">StartThreads</a> <a name="startthreads" id="startthreads">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created on startup</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartThreads <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code></td></tr>
+</table>
+ <p>Number of threads created on startup. As the
+ number of threads is dynamically controlled depending on the
+ load, (see
+ <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>,
+ <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code>,
+ <code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code>)
+ there is usually little reason to adjust this
+ parameter.</p>
+
+ <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
+ <code>StartThreads 50</code> and, since there is only a single
+ process, this is the total number of threads created at startup to
+ serve requests.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ThreadLimit" id="ThreadLimit">ThreadLimit</a> <a name="threadlimit" id="threadlimit">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the upper limit on the configurable number of threads
+per child process</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadLimit <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code></td></tr>
+</table>
+ <p>This directive sets the maximum configured value for <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the lifetime
+ of the Apache httpd process. Any attempts to change this directive
+ during a restart will be ignored, but <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> can be modified
+ during a restart up to the value of this directive.</p>
+
+ <p>Special care must be taken when using this directive. If
+ <code class="directive">ThreadLimit</code> is set to a value much higher
+ than <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>,
+ extra unused shared memory will be allocated. If both
+ <code class="directive">ThreadLimit</code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> are set to values
+ higher than the system can handle, Apache httpd may not start or the
+ system may become unstable. Do not set the value of this directive
+ any higher than your greatest predicted setting of <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the
+ current run of Apache httpd.</p>
+
+ <p>The default value for <code class="directive">ThreadLimit</code> is
+ <code>1920</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
+ <code>64</code> when used with the others.</p>
+
+ <div class="note"><h3>Note</h3>
+ <p>There is a hard limit of <code>ThreadLimit 20000</code> (or
+ <code>ThreadLimit 100000</code> with <code class="module"><a href="../mod/event.html">event</a></code>,
+ <code>ThreadLimit 15000</code> with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>)
+ compiled into the server. This is intended to avoid nasty effects
+ caused by typos. To increase it even further past this limit, you
+ will need to modify the value of MAX_THREAD_LIMIT in the mpm
+ source file and rebuild the server.</p>
+ </div>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ThreadsPerChild" id="ThreadsPerChild">ThreadsPerChild</a> <a name="threadsperchild" id="threadsperchild">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created by each child process</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadsPerChild <var>number</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code></td></tr>
+</table>
+ <p>This directive sets the number of threads created by each
+ child process. The child creates these threads at startup and
+ never creates more. If using an MPM like <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>,
+ where there is only one child process, this number should be high
+ enough to handle the entire load of the server. If using an MPM
+ like <code class="module"><a href="../mod/worker.html">worker</a></code>, where there are multiple child processes,
+ the <em>total</em> number of threads should be high enough to handle
+ the common load on the server.</p>
+
+ <p>The default value for <code class="directive">ThreadsPerChild</code> is
+ <code>64</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
+ <code>25</code> when used with the others.</p>
+
+ <p>The value of <code class="directive">ThreadsPerChild</code> can not exceed the
+ value of <code class="directive"><a href="#threadlimit">ThreadLimit</a></code>. If a
+ higher value is configured, it will be automatically reduced at start-up
+ and a warning will be logged. The relationship between these 2 directives
+ is explained in <code class="directive"><a href="#threadlimit">ThreadLimit</a></code>.</p>
+
+</div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="directive-section"><h2><a name="ThreadStackSize" id="ThreadStackSize">ThreadStackSize</a> <a name="threadstacksize" id="threadstacksize">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The size in bytes of the stack used by threads handling
+client connections</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadStackSize <var>size</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>65536 on NetWare; varies on other operating systems</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
+<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
+<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr>
+<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.1 and later</td></tr>
+</table>
+ <p>The <code class="directive">ThreadStackSize</code> directive sets the
+ size of the stack (for autodata) of threads which handle client
+ connections and call modules to help process those connections.
+ In most cases the operating system default for stack size is
+ reasonable, but there are some conditions where it may need to be
+ adjusted:</p>
+
+ <ul>
+ <li>On platforms with a relatively small default thread stack size
+ (e.g., HP-UX), Apache httpd may crash when using some third-party modules
+ which use a relatively large amount of autodata storage. Those
+ same modules may have worked fine on other platforms where the
+ default thread stack size is larger. This type of crash is
+ resolved by setting <code class="directive">ThreadStackSize</code> to a
+ value higher than the operating system default. This type of
+ adjustment is necessary only if the provider of the third-party
+ module specifies that it is required, or if diagnosis of an Apache httpd
+ crash indicates that the thread stack size was too small.</li>
+
+ <li>On platforms where the default thread stack size is
+ significantly larger than necessary for the web server
+ configuration, a higher number of threads per child process
+ will be achievable if <code class="directive">ThreadStackSize</code> is
+ set to a value lower than the operating system default. This type
+ of adjustment should only be made in a test environment which allows
+ the full set of web server processing to be exercised, as there
+ may be infrequent requests which require more stack to process.
+ The minimum required stack size strongly depends on the modules
+ used, but any change in the web server configuration can invalidate
+ the current <code class="directive">ThreadStackSize</code> setting.</li>
+
+ <li>On Linux, this directive can only be used to increase the default
+ stack size, as the underlying system call uses the value as a
+ <em>minimum</em> stack size. The (often large) soft limit for
+ <code>ulimit -s</code> (8MB if unlimited) is used as the default stack
+ size.</li>
+ </ul>
+
+ <div class="note">It is recommended to not reduce <code class="directive">ThreadStackSize</code>
+ unless a high number of threads per child process is needed. On some
+ platforms (including Linux), a setting of 128000 is already too low and
+ causes crashes with some common modules.</div>
+
+</div>
+</div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
+<a href="../en/mod/mpm_common.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../fr/mod/mpm_common.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
+<a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
+</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Libera.chat, or sent to our <a href="https://httpd.apache.org/lists.html">mailing lists</a>.</div>
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