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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@209162 c90b9560-bf6c-de11-be94-00142212c4b1
436 lines
14 KiB
XML
436 lines
14 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.6 $ -->
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<section id="apc.configuration">
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&reftitle.runtime;
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&extension.runtime;
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<para>
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Although the default APC settings are fine for many installations, serious
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users should consider tuning the following parameters.
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</para>
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<para>
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There are two main decisions you have to make. First, how much shared
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memory do you want to set aside for APC, and second, whether you want APC
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to check if a file has been modified on every request. The two ini
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directives involved here are <literal>apc.shm_size</literal> and
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<literal>apc.stat</literal>. Read the sections on these two directives
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carefully below.
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</para>
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<para>
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Once you have a running server, you should copy the
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<literal>apc.php</literal> script that comes with the extension to
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somewhere in your docroot and load it up in your browser. It provides
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you with a detailed look at what is happening in your cache. If you
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have GD enabled in PHP, it will even have pretty graphs. First thing
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to check is of course that it is actually caching files. Assuming it is
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working you should then pay close attention to the <literal>Cache full
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count</literal> number on the left. That tells you the number of times
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the cache has filled up and has had to forcefully clean up any entries
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not accessed within the last <literal>apc.ttl</literal> seconds. You
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should configure your cache to minimize this number. If you are constantly
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filling your cache, the resulting cache churn is going to hurt performance.
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You should either set more memory aside for APC, or use
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<literal>apc.filters</literal> to cache fewer scripts.
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</para>
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<para>
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<table>
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<title>APC configuration options</title>
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<tgroup cols="4">
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<thead>
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<row>
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<entry>Name</entry>
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<entry>Default</entry>
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<entry>Changeable</entry>
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<entry>Changelog</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>apc.enabled</entry>
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<entry>"1"</entry>
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<entry>PHP_INI_ALL</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.shm_segments</entry>
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<entry>"1"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.shm_size</entry>
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<entry>"30"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.optimization</entry>
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<entry>"0"</entry>
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<entry>PHP_INI_ALL</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.num_files_hint</entry>
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<entry>"1000"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.ttl</entry>
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<entry>"0"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.gc_ttl</entry>
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<entry>"3600"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.cache_by_default</entry>
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<entry>"1"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.filters</entry>
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<entry>NULL</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.mmap_file_mask</entry>
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<entry>NULL</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.slam_defense</entry>
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<entry>"0"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.file_update_protection</entry>
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<entry>"2"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry></entry>
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</row>
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<row>
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<entry>apc.enable_cli</entry>
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<entry>"0"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry>> APC 3.0.6</entry>
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</row>
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<row>
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<entry>apc.max_file_size</entry>
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<entry>"1M"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry>> APC 3.0.6</entry>
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</row>
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<row>
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<entry>apc.stat</entry>
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<entry>"1"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry>> APC 3.0.9</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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&ini.php.constants;
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</para>
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&ini.descriptions.title;
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<para>
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<variablelist>
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<varlistentry id="ini.apc.enabled">
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<term>
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<parameter>apc.enabled</parameter>
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<type>boolean</type>
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</term>
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<listitem>
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<para>
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<literal>apc.enabled</literal> can be set to 0 to disable APC. This is
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primarily useful when APC is statically compiled
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into PHP, since there is no other way to disable
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it (when compiled as a DSO, the <literal>extension</literal>
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line in <literal>php.ini</literal> can just be commented-out).
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.shm-segments">
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<term>
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<parameter>apc.shm_segments</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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The number of shared memory segments to allocate
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for the compiler cache. If APC is running out of
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shared memory but you have already set
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<literal>apc.shm_size</literal> as high as your system allows, you
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can try raising this value.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.shm-size">
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<term>
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<parameter>apc.shm_size</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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The size of each shared memory segment in MB.
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By default, some systems (including most BSD
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variants) have very low limits on the size of a
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shared memory segment.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.optimization">
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<term>
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<parameter>apc.optimization</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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The optimization level. Zero disables the
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optimizer, and higher values use more aggressive
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optimizations. Expect very modest speed
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improvements. This is experimental.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.num-files-hint">
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<term>
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<parameter>apc.num_files_hint</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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A "hint" about the number of distinct source files
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that will be included or requested on your web
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server. Set to zero or omit if you're not sure;
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this setting is mainly useful for sites that have
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many thousands of source files.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.ttl">
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<term>
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<parameter>apc.ttl</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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The number of seconds a cache entry is allowed to
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idle in a slot in case this cache entry slot is
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needed by another entry. Leaving this at zero
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means that your cache could potentially fill up
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with stale entries while newer entries won't be
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cached.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.gc-ttl">
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<term>
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<parameter>apc.gc_ttl</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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The number of seconds that a cache entry may
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remain on the garbage-collection list. This value
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provides a fail-safe in the event that a server
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process dies while executing a cached source file;
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if that source file is modified, the memory
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allocated for the old version will not be
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reclaimed until this TTL reached. Set to zero to
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disable this feature.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.cache-by-default">
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<term>
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<parameter>apc.cache_by_default</parameter>
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<type>boolean</type>
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</term>
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<listitem>
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<para>
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On by default, but can be set to off and used in
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conjunction with positive <literal>apc.filters</literal> so that files
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are only cached if matched by a positive filter.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.filters">
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<term>
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<parameter>apc.filters</parameter>
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<type>string</type>
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</term>
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<listitem>
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<para>
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A comma-separated list of POSIX extended regular
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expressions. If any pattern matches the source
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filename, the file will not be cached. Note that
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the filename used for matching is the one passed
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to include/require, not the absolute path. If the
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first character of the expression is a <literal>+</literal> then the
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expression will be additive in the sense that any
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files matched by the expression will be cached, and
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if the first character is a <literal>-</literal> then anything matched
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will not be cached. The <literal>-</literal> case is the default, so
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it can be left off.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.mmap-file-mask">
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<term>
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<parameter>apc.mmap_file_mask</parameter>
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<type>string</type>
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</term>
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<listitem>
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<para>
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If compiled with MMAP support by using <literal>--enable-mmap</literal>
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this is the mktemp-style file_mask to pass to the
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mmap module for determing whether your mmap'ed memory
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region is going to be file-backed or shared memory
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backed. For straight file-backed mmap, set it to
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something like <literal>/tmp/apc.XXXXXX</literal>
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(exactly 6 <literal>X</literal>s).
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To use POSIX-style shm_open/mmap put a <literal>.shm</literal>
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somewhere in your mask. e.g. <literal>/apc.shm.XXXXXX</literal>
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You can also set it to <literal>/dev/zero</literal> to use your
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kernel's <literal>/dev/zero</literal> interface to anonymous mmap'ed
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memory. Leaving it undefined will force an anonymous mmap.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.slam-defense">
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<term>
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<parameter>apc.slam_defense</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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On very busy servers whenever you start the server or
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modify files you can create a race of many processes
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all trying to cache the same file at the same time.
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This option sets the percentage of processes that will
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skip trying to cache an uncached file. Or think of it
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as the probability of a single process to skip caching.
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For example, setting <literal>apc.slam_defense</literal>
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to <literal>75</literal> would mean that there is
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a 75% chance that the process will not cache an uncached
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file. So, the higher the setting the greater the defense
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against cache slams. Setting this to <literal>0</literal>
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disables this feature.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.file-update-protection">
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<term>
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<parameter>apc.file_update_protection</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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When you modify a file on a live web server you really
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should do so in an atomic manner. That is, write to a
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temporary file and rename (<literal>mv</literal>) the file into its
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permanent position when it is ready. Many text editors, cp, tar and
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other such programs don't do this. This means that there
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is a chance that a file is accessed (and cached) while it
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is still being written to. This <literal>apc.file_update_protection</literal>
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setting puts a delay on caching brand new files. The
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default is 2 seconds which means that if the modification
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timestamp (<literal>mtime</literal>) on a file shows that it is less than 2
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seconds old when it is accessed, it will not be cached.
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The unfortunate person who accessed this half-written file
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will still see weirdness, but at least it won't persist.
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If you are certain you always atomically update your files
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by using something like rsync which does this correctly, you
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can turn this protection off by setting it to 0. If you
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have a system that is flooded with io causing some update
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procedure to take longer than 2 seconds, you may want to
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increase this a bit.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.enable-cli">
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<term>
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<parameter>apc.enable_cli</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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Mostly for testing and debugging. Setting this enables APC
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for the CLI version of PHP. Normally you wouldn't want to
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create, populate and tear down the APC cache on every CLI
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request, but for various test scenarios it is handy to be
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able to enable APC for the CLI version of APC easily.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.max_file_size">
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<term>
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<parameter>apc.max_file_size</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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Prevent files larger than this value from getting cached. Defaults to
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1M.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="ini.apc.stat">
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<term>
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<parameter>apc.stat</parameter>
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<type>integer</type>
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</term>
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<listitem>
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<para>
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Be careful if you change this setting. The default is for this to be On
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which means that APC will stat (check) the script on each request to see
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if it has been modified. If it has been modified it will recompile and
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cache the new version. If you turn this setting off, it will not check.
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That means that in order to have changes become active you need to
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restart your web server. On a production server where you rarely
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change the code, turning stats off can produce a significant performance
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boost.
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</para>
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<para>
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For included/required files this option applies as well, but note that
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if you are using relative path includes (any path that doesn't start
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with / on Unix) APC has to check in order to uniquely identify the file.
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If you use absolute path includes APC can skip the stat and use that
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absolute path as the unique identifier for the file.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</section>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"../../../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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