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From sl...@apache.org
Subject cvs commit: httpd-2.0/docs/manual/mod mpm_common.xml prefork.xml
Date Tue, 26 Feb 2002 19:00:40 GMT
slive       02/02/26 11:00:40

  Added:       docs/manual/mod mpm_common.xml prefork.xml
  Log:
  Start converting the mpm documentation.
  
  Revision  Changes    Path
  1.1                  httpd-2.0/docs/manual/mod/mpm_common.xml
  
  Index: mpm_common.xml
  ===================================================================
  <?xml version="1.0"?>
  <?xml-stylesheet type="text/xsl" href="../style/manual.xsl"?>
  <modulesynopsis>
  
  <name>mpm_common</name>
  <description>A collection of directives that are implemented by
  more than one multi-processing module (MPM)</description>
  <status>MPM</status>
  
  <directivesynopsis>
  <name>CoreDumpDirectory</name>
  <description>Sets the directory where Apache attempts to
  switch before dumping core</description>
  <syntax>CoreDumpDirectory <em>directory</em></syntax>
  <default>CoreDumpDirectory <em>ServerRoot</em></default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module><module>mpm_winnt</module>
  </modulelist>
  
  <usage>
  
      <p>This controls the directory to which Apache attempts to
      switch before dumping core. The default is in the 
      <directive module="core">ServerRoot</directive> directory, however
      since this should not be writable by the user the server runs
      as, core dumps won't normally get written. If you want a core
      dump for debugging, you can use this directive to place it in a
      different location.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>Group</name>
  <description>Sets the group under which the server will answer
  requests</description>
  <syntax>Group <em>unix-group</em></syntax>
  <default>Group #-1</default>
  <contextlist><context>server config</context><context>virtual host</context>
  </contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module></modulelist>
  
  <usage>
      <p>The <directive>Group</directive> directive sets the group under
      which the server will answer requests. In order to use this
      directive, the stand-alone server must be run initially as root.
      <em>Unix-group</em> is one of:</p>
  
      <dl>
        <dt>A group name</dt>
  
        <dd>Refers to the given group by name.</dd>
  
        <dt># followed by a group number.</dt>
  
        <dd>Refers to a group by its number.</dd>
      </dl>
      <p>It is recommended that you set up a new group specifically for
      running the server. Some admins use user <code>nobody</code>,
      but this is not always possible or desirable.</p>
  
      <p>Note: if you start the server as a non-root user, it will
      fail to change to the specified group, and will instead
      continue to run as the group of the original user.</p>
  
      <p>Special note: Use of this directive in &lt;VirtualHost&lt; is
      no longer supported. To implement the <a
      href="../suexec.html">suEXEC wrapper</a> with Apache 2.0, use the
      <directive module="mod_suexec">SuexecUserGroup</directive>
      directive. SECURITY: See <directive
      module="mpm_common">User</directive> for a discussion of the
      security considerations.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>PidFile</name>
  <description>Sets the file where the server records the process ID
  of the daemon</description>
  <syntax>PidFile <em>filename</em></syntax>
  <default>PidFile logs/httpd.pid</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchilde</module>
  <module>prefork</module><module>mpm_winnt</module>
  </modulelist>
  
  <usage>
      <p>The <directive>PidFile</directive> directive sets the file to
      which the server records the process id of the daemon. If the
      filename does not begin with a slash (/) then it is assumed to be
      relative to the <directive module="core">ServerRoot</directive>.</p>
  
      <p>It is often useful to be able to send the server a signal,
      so that it closes and then reopens its <directive
      module="core">ErrorLog</directive> and TransferLog, and
      re-reads its configuration files. This is done by sending a
      SIGHUP (kill -1) signal to the process id listed in the
      PidFile.</p>
  
      <p>The PidFile is subject to the same warnings about log file
      placement and <a
      href="../misc/security_tips.html#serverroot">security</a>.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>Listen</name>
  <description>Sets the IP addresses and ports that the server
  listens to</description>
  <syntax>Listen [<em>IP-address</em>:]<em>portnumber</em></syntax>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module><module>mpm_winnt</module>
  </modulelist>
  
  <usage>
      <p>The <directive>Listen</directive> directive instructs Apache to
      listen to only specific IP addresses or ports; by default it
      responds to requests on all IP interfaces. The Listen directive 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.</p>
  
      <p>The Listen 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 Listen 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>
  <example>
     Listen 80<br />
     Listen 8000
  </example>
      To make the server accept connections on two specified
      interfaces and port numbers, use 
  <example>
     Listen 192.170.2.1:80<br />
     Listen 192.170.2.5:8000
  </example>
      IPv6 addresses must be surrounded in square brackets, as in the
      following example:
  <example>
     Listen [fe80::a00:20ff:fea7:ccea]:80
  </example>
  </usage>
  
  <seealso><a href="../dns-caveats.html">DNS Issues</a></seealso>
  <seealso><a href="../bind.html">Setting
      which addresses and ports Apache uses</a></seealso>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>ListenBackLog</name>
  <description>Maximum length of the queue of pending connections</description>
  <syntax>ListenBacklog <em>backlog</em></syntax>
  <default>ListenBacklog 511</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module><module>mpm_winnt</module>
  </modulelist>
  
  <usage>
      <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>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>LockFile</name>
  <description>Location of the accept serialization lock file</description>
  <syntax>LockFile <em>filename</em></syntax>
  <default>LockFile logs/accept.lock</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module></modulelist>
  
  <usage>
      <p>The <directive>LockFile</directive> directive sets the path to
      the lockfile used when Apache is compiled with either
      USE_FCNTL_SERIALIZED_ACCEPT or USE_FLOCK_SERIALIZED_ACCEPT. This
      directive should normally be left at its default value. The main
      reason for changing it is if the <code>logs</code> directory is
      NFS mounted, since <strong>the lockfile must be stored on a local
      disk</strong>.  The PID of the main server process is
      automatically appended to the filename.</p>
  
      <p><strong>SECURITY:</strong> It is best to avoid putting this
      file in a world writable directory such as
      <code>/var/tmp</code> because someone could create a denial of
      service attack and prevent the server from starting by creating
      a lockfile with the same name as the one the server will try to
      create.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>MaxClients</name>
  <description>Maximum number of child processes that will be created
  to serve requests</description>
  <syntax>MaxClients <em>number</em></syntax>
  <default>>MaxClients
      8 (with threads) MaxClients 256</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>prefork</module>
  </modulelist>
  
  <usage>
      <p>The <directive>MaxClients</directive> directive sets the limit
      on the number of child processes that will be created to serve
      requests. When the server is built without threading, no more than
      this number of clients can be served simultaneously. To configure
      more than 256 clients with the prefork MPM, you must use the
      <directive module="mpm_common">ServerLimit</directive> directive.
      To configure more than 1024 clients with the worker MPM, you must
      use the <directive module="mpm_common">ServerLimit</directive> and
      <directive module="mpm_common">ThreadLimit</directive> directives.</p>
  
      <p>Any connection attempts over the
      <directive>MaxClients</directive> limit will normally be queued,
      up to a number based on the <directive module="mpm_common"
      >ListenBacklog</directive> directive. Once a child
      process is freed at the end of a different request, the connection
      will then be serviced.</p>
  
      <p>When the server is compiled with threading, then the maximum
      number of simultaneous requests that can be served is obtained
      from the value of this directive multiplied by
      <directive module="mpm_common">ThreadsPerChild</directive>.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>MaxRequestPerChild</name>
  <description>Limit on the number of requests that an individual child server
  will handle during its life</description>
  <syntax>MaxRequestsPerChild <em>number</em></syntax>
  <default>MaxRequestsPerChild 10000</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module><module>mpm_winnt</module>
  </modulelist>
  
  <usage>
      <p>The <directive>MaxRequestsPerChild</directive> directive sets
      the limit on the number of requests that an individual child
      server process will handle. After
      <directive>MaxRequestsPerChild</directive> requests, the child
      process will die. If <directive>MaxRequestsPerChild</directive> is
      0, then the process will never expire.</p>
  
      <p>Setting <directive>MaxRequestsPerChild</directive> to a
      non-zero limit has two beneficial effects:</p>
  
      <ul>
        <li>it limits the amount of memory that process can consume
        by (accidental) memory leakage;</li>
  
        <li>by giving processes a finite lifetime, it helps reduce
        the number of processes when the server load reduces.</li>
      </ul>
  
      <p><strong>NOTE:</strong> For <em>KeepAlive</em> requests,
only
      the first request is counted towards this limit. In effect, it
      changes the behavior to limit the number of
      <em>connections</em> per child.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>MaxSpareThreads</name>
  <description>Maximum number of idle threads</description>
  <syntax>MaxSpareThreads <em>number</em></syntax>
  <default>MaxSpareThreads 10 (Perchild) or 500 (worker)</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  </modulelist>
  
  <usage>
      <p>Maximum number of idle threads. Different MPMs deal with this
      directive differently. <module>perchild</module> monitors the
      number of idle threads on a per-child basis. If there are too many
      idle threads in that child, the server will begin to kill threads
      within that child.</p>
  
      <p><module>worker</module> deals 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.</p>
  
  </usage>
  <seealso><directive module="mpm_common">MinSpareThreads</directive></seealso>
  <seealso><directive module="mpm_common">StartServers</directive></seealso>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>MaxThreadsPerChild</name>
  <description>Maximum number of threads per child process</description>
  <syntax>MaxThreadsPerChild <em>number</em></syntax>
  <default>MaxThreadsPerChild 64</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  </modulelist>
  
  <usage>
      <p>Maximum number of threads per child. For MPMs with a
      variable number of threads per child, this directive sets the
      maximum number of threads that will be created in each child
      process. To increase this value beyond its default, it is
      necessary to change the value of the compile-time define
      <code>HARD_THREAD_LIMIT</code> and recompile the server.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>MinSpareThreads</name>
  <description>Minimum number of idle threads available to handle request
  spikes</description>
  <syntax>MinSpareServers <em>number</em></syntax>
  <default>MinSpareThreads 5 (Perchild) or 250 (worker)</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  </modulelist>
  
  <usage>
      <p>Minimum number of idle threads to handle request spikes.
      Different MPMs deal with this directive
      differently. <module>perchild</module> monitors the number of idle
      threads on a per-child basis. If there aren't enough idle threads
      in that child, the server will begin to create new threads within
      that child.</p>
  
      <p><module>worker</module> deals 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 number.</p>
  </usage>
  <seealso><directive module="mpm_common">MaxSpareThreads</directive></seealso>
  <seealso><directive module="mpm_common">StartServers</directive></seealso>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>NumServers</name>
  <description>Total number of children alive at the same time</description>
  <syntax>NumServers <em>number</em></syntax>
  <default>NumServers 2</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>perchild</module></modulelist>
  
  <usage>
      <p>Number of children alive at the same time. MPMs that use
      this directive do not dynamically create new child processes so
      this number should be large enough to handle the requests for
      the entire site.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>ScoreBoardFile</name>
  <description>Location of the file used to store coordination data for
  the child processes</description>
  <syntax>ScoreBoardFile <em>file-path</em></syntax>
  <default>ScoreBoardFile logs/apache_status</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module></modulelist>
  
  <usage>
      <p>The <directive>ScoreBoardFile</directive> directive is required
      on some architectures to place a file that the server will use to
      communicate between its children and the parent. The easiest way
      to find out if your architecture requires a scoreboard file is to
      run Apache and see if it creates the file named by the
      directive. If your architecture requires it then you must ensure
      that this file is not used at the same time by more than one
      invocation of Apache.</p>
  
      <p>If you have to use a <directive>ScoreBoardFile</directive> 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>
  </usage>
  <seealso><a
      href="../stopping.html">Stopping and Restarting Apache</a></seealso>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SendBufferSize</name>
  <description>TCP buffer size</description>
  <syntax>SendBufferSize <em>bytes</em></syntax>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module><module>mpm_winnt</module>
  </modulelist>
  
  <usage>
      <p>The server will set the TCP buffer size to the number of bytes
      specified. Very useful to increase past standard OS defaults on
      high speed high latency (<em>i.e.</em>, 100ms or so, such as
      transcontinental fast pipes).</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>ServerLimit</name>
  <description>Upper limit on configurable number of processes</description>
  <syntax>ServerLimit <em>number</em></syntax>
  <default>ServerLimit 256 (prefork), ServerLimit 16 (worker)</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>prefork</module>
  </modulelist>
  
  <usage>
      <p>For the <module>prefork</module> MPM, this directive sets the
      maximum configured value for <directive
      module="mpm_common">MaxClients</directive> for the lifetime of the
      Apache process.  For the worker MPM, this directive in combination
      with <directive module="mpm_common">ThreadLimit</directive> sets
      the maximum configured value for <directive
      module="mpm_common">MaxClients</directive> for the lifetime of the
      Apache process.  Any attempts to change this directive during a
      restart will be ignored, but <directive
      module="mpm_common">MaxClients</directive> can be modified during
      a restart.</p>
  
      <p>Special care must be taken when using this directive.  If
      <directive>ServerLimit</directive> is set to a value much higher
      than necessary, extra, unused shared memory will be allocated.  If
      both <directive>ServerLimit</directive> and <directive
      module="mpm_common">MaxClients</directive> are set to values
      higher than the system can handle, Apache may not start or the
      system may become unstable.</p>
  
      <p>With the <module>prefork</module> MPM, use this directive only
      if you need to set <directive
      module="mpm_common">MaxClients</directive> higher higher than 256.
      Do not set the value of this directive any higher than what you
      might want to set <directive
      module="mpm_common">MaxClients</directive> to.</p>
  
      <p>With the <module>worker</module> MPM, use this directive only
      if your <directive module="mpm_common">MaxClients</directive> and
      <directive module="mpm_common">ThreadsPerChild</directive>
      settings require more than 16 server processes.  Do not set the
      value of this directive any higher than the number of server
      processes required by what you may want for <directive
      module="mpm_common">MaxClients </directive> and <directive
      module="mpm_common">ThreadsPerChild</directive>.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>StartServers</name>
  <description>Number of child server processes created at startup</description>
  <syntax>StartServers <em>number</em></syntax>
  <default>StartServers 5</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module></modulelist>
  
  <usage>
      <p>The <directive>StartServers</directive> directive sets the
      number of child server processes created on startup. As the number
      of processes is dynamically controlled depending on the load,
      there is usually little reason to adjust this parameter.</p>
  </usage>
  <seealso><directive module="mpm_common">MinSpareThreads</directive></seealso>
  <seealso><directive module="mpm_common">MaxSpareThreads</directive></seealso>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>StartThreads</name>
  <description>Nubmer of threads each child creates on startup</description>
  <syntax>StartThreads <em>number</em></syntax>
  <default>StartThreads 5</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>perchild</module></modulelist>
  
  <usage>
      <p>Number of threads each child creates on startup. As the
      number of threads is dynamically controlled depending on the
      load, there is usually little reason to adjust this
      parameter.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>ThreadLimit</name>
  <description>Sets the upper limit on the configurable number of threads
  per child process</description>
  <syntax>ThreadLimit <em>number</em></syntax>
  <default>ThreadLimit 64</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module></modulelist>
  
  <usage>
      <p>This directive sets the maximum configured value for <directive
      module="mpm_common">ThreadsPerChild</directive> for the lifetime
      of the Apache process.  Any attempts to change this directive
      during a restart will be ignored, but <directive
      module="mpm_common">ThreadsPerChild</directive> 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
      <directive>ThreadLimit</directive> is set to a value much higher
      than <directive module="mpm_common">ThreadsPerChild</directive>,
      extra unused shared memory will be allocated.  If both
      <directive>ThreadLimit</directive> and <directive
      module="mpm_common">ThreadsPerChild</directive> are set to values
      higher than the system can handle, Apache may not start or the
      system may become unstable.</p>
  
      <p>Use this directive only if you need to set <directive
      module="mpm_common">ThreadsPerChild</directive> higher than 64.  Do
      not set the value of this directive any higher than what you might
      want to set <directive
      module="mpm_common">ThreadsPerChild</directive> to.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>ThreadsPerChild</name>
  <description>Number of threads created by each child process</description>
  <syntax>ThreadsPerChild <em>number</em></syntax>
  <default>ThreadsPerChild 50</default>
  <contextlist><context>server config</context></contextlist>
  <modulelist><module>worker</module><module>mpm_winnt</module>
  </modulelist>
  
  <usage>
      <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 mpmt_winnt, 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 worker, where there are multiple child processes, the
      total number of threads should be high enough to handle the
      common load on the server.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>User</name>
  <description>The userid under which the server will answer
  requests</description>
  <syntax>User <em>unix-userid</em></syntax>
  <default>User #-1</default>
  <contextlist><context>server config</context><context>virtual host</context>
  </contextlist>
  <modulelist><module>worker</module><module>perchild</module>
  <module>prefork</module></modulelist>
  
  <usage>
      <p>The <directive>User</directive> directive sets the userid as
      which the server will answer requests. In order to use this
      directive, the standalone server must be run initially as
      root. <em>Unix-userid</em> is one of:</p>
  
      <dl>
        <dt>A username</dt>
  
        <dd>Refers to the given user by name.</dd>
  
        <dt># followed by a user number.</dt>
  
        <dd>Refers to a user by their number.</dd>
      </dl>
  
      <p>The user should have no privileges which result in it being
      able to access files which are not intended to be visible to the
      outside world, and similarly, the user should not be able to
      execute code which is not meant for httpd requests. It is
      recommended that you set up a new user and group specifically for
      running the server. Some admins use user <code>nobody</code>, but
      this is not always possible or desirable. For example
      <module>mod_proxy</module>'s cache, when enabled, must be
      accessible to this user (see <directive
      module="mod_proxy">CacheRoot</directive>).</p>
  
      <p>Notes: If you start the server as a non-root user, it will
      fail to change to the lesser privileged user, and will instead
      continue to run as that original user. If you do start the
      server as root, then it is normal for the parent process to
      remain running as root.</p>
  
      <p>Special note: Use of this directive in <directive module="core"
      type="section">VirtualHost</directive> is no longer supported. To
      configure your server for <a href="mod_suexec.html">suexec</a> use
      <directive module="mod_suexec">SuexecUserGroup</directive>.</p>
  
  <note><title>Security</title> <p>Don't set <directive>User</directive>
  (or <directive module="mpm_common">Group</directive>) to
  <code>root</code> unless you know exactly what you are doing, and what
  the dangers are.</p></note>
  </usage>
  </directivesynopsis>
  
  </modulesynopsis>
  
  
  1.1                  httpd-2.0/docs/manual/mod/prefork.xml
  
  Index: prefork.xml
  ===================================================================
  <?xml version="1.0"?>
  <?xml-stylesheet type="text/xsl" href="../style/manual.xsl"?>
  <modulesynopsis>
  <name>prefork</name>
  <description>Implements a non-threaded, pre-forking web server</description>
  <status>MPM</status>
  <sourcefile>prefork.c</sourcefile>
  <identifier>mpm_prefork_module</identifier>
  
  <summary>
      <p>This Multi-Processing Module (MPM) implements a
      non-threaded, pre-forking web server which handles request in a
      manner very similar to the default behavior of Apache 1.3 on
      Unix.</p>
  
      <p>A single control process is responsible for launching child
      processes which listen for connections and serve them when they
      arrive. Apache always tries to maintain several <em>spare</em>
      or idle server processes, which stand ready to serve incoming
      requests. In this way, clients do not need to wait for a new
      child processes to be forked before their requests can be
      served.</p>
  
      <p>The <directive module="mpm_common">StartServers</directive>,
      <directive module="prefork">MinSpareServers</directive>,
      <directive module="prefork">MaxSpareServers</directive>, and
      <directive module="mpm_common">MaxClients</directive> regulate how
      the parent process creates children to serve requests. In general,
      Apache is very self-regulating, so most sites do not need to
      adjust these directives from their default values. Sites which
      need to serve more than 256 simultaneous requests may need to
      increase <directive module="mpm_common">MaxClients</directive>,
      while sites with limited memory may need to decrease <directive
      module="mpm_common">MaxClients</directive> to keep the server from
      thrashing (swapping memory to disk and back). More information
      about tuning process creation is provided in the <a
      href="../misc/perf-tuning.html">performance hints</a>
      documentation.</p>
  
      <p>While the parent process is usually started as root under Unix
      in order to bind to port 80, the child processes are launched by
      Apache as a less-privileged user. The <directive
      module="mpm_common">User</directive> and <directive
      module="mpm_common">Group</directive> directives are used to set
      the privileges of the Apache child processes. The child processes
      must be able to read all the content that will be served, but
      should have as few privileges beyond that as possible. In
      addition, unless <a href="../suexec.html">suexec</a> is used,
      these directives also set the privileges which will be inherited
      by CGI scripts.</p>
  
      <p><directive module="mpm_common">MaxRequestsPerChild</directive>
      controls how frequently the server recycles processes by killing
      old ones and launching new ones.</p>
  </summary>
  <seealso><a href="../bind.html">Setting which addresses and
      ports Apache uses</a></seealso>
  
  <directivesynopsis location="mpm_common">
  <name>CoreDumpDirectory</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>PidFile</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>Listen</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>ListenBacklog</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>LockFile</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>MaxRequestsPerChild</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>MaxSpareServers</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>MinSpareServers</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>ScoreBoardFile</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>SendBufferSize</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>ServerLimit</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>StartServers</name>
  </directivesynopsis>
  
  <directivesynopsis location="mpm_common">
  <name>User</name>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>AcceptMutex</name>
  <description>Method that Apache uses to serialize multiple children
  accepting requests on network sockets</description>
  <syntax>AcceptMutex default|<em>method</em></syntax>
  <default>AcceptMutex default</default>
  <contextlist><context>server config</context></contextlist>
  
  <usage>
      <p>The <directive>AcceptMutex</directive> directives sets the
      method that Apache uses to serialize multiple children accepting
      requests on network sockets. Prior to Apache 2.0, the method was
      selectable only at compile time. The optimal method to use is
      highly architecture and platform dependent. For further details,
      see the <a href="../misc/perf-tuning.html">performance tuning</a>
      documentation.</p>
  
      <p>If this directive is set to <code>default</code>, then the
      compile-time selected default will be used. Other possible
      methods are listed below. Note that not all methods are
      available on all platforms. If a method is specified which is
      not available, a message will be written to the error log
      listing the available methods.</p>
  
      <dl>
        <dt><code>flock</code></dt>
  
        <dd>uses the <code>flock(2)</code> system call to lock the
        file defined by the <directive module="mpm_common"
        >LockFile</directive> directive.</dd>
  
        <dt><code>fcntl</code></dt>
  
        <dd>uses the <code>fnctl(2)</code> system call to lock the
        file defined by the <directive module="mpm_common"
        >LockFile</directive> directive.</dd>
  
        <dt><code>sysvsem</code></dt>
  
        <dd>uses SySV-style semaphores to implement the mutex.</dd>
  
        <dt><code>pthread</code></dt>
  
        <dd>uses POSIX mutexes as implemented by the POSIX Threads
        (PThreads) specification.</dd>
      </dl>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>MaxSpareServers</name>
  <description>Maximum number of idle child server processes</description>
  <syntax>MaxSpareServers <em>number</em><br /></syntax>
  <default>MaxSpareServers 10</default>
  <contextlist><context>server config</context></contextlist>
  
  <usage>
      <p>The <directive>MaxSpareServers</directive> directive sets the
      desired maximum number of <em>idle</em> child server processes. An
      idle process is one which is not handling a request. If there are
      more than MaxSpareServers idle, then the parent process will kill
      off the excess processes.</p>
  
      <p>Tuning of this parameter should only be necessary on very
      busy sites. Setting this parameter to a large number is almost
      always a bad idea.</p>
  </usage>
  <seealso><directive module="prefork">MinSpareServers</directive></seealso>
  <seealso><directive module="mpm_common">StartServers</directive></seealso>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>MinSpareServers</name>
  <description>Minimum number of idle child server processes</description>
  <syntax>MinSpareServers <em>number</em></syntax>
  <default>MinSpareServers  5</default>
  <contextlist><context>server config</context></contextlist>
  
  <usage>
      <p>The <directive>MinSpareServers</directive> directive sets the
      desired minimum number of <em>idle</em> child server processes. An
      idle process is one which is not handling a request. If there are
      fewer than MinSpareServers idle, then the parent process creates
      new children at a maximum rate of 1 per second.</p>
  
      <p>Tuning of this parameter should only be necessary on very
      busy sites. Setting this parameter to a large number is almost
      always a bad idea.</p>
  
      <p>This directive has no effect on Microsoft Windows.</p>
  </usage>
  <seealso><directive module="prefork">MaxSpareServers</directive></seealso>
  <seealso><directive module="mpm_common">StartServers</directive></seealso>
  </directivesynopsis>
  
  </modulesynopsis>
  
  
  
  

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