mirror of
https://github.com/sigmasternchen/php-doc-en
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383 lines
13 KiB
XML
383 lines
13 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<section xml:id="apcu.configuration" xmlns="http://docbook.org/ns/docbook">
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&reftitle.runtime;
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&extension.runtime;
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<para>
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Although the default APCu 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 is one decision to be made configuring APCu.
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How much memory is going to be allocated to APCu.
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The ini directive that controls this is <literal>apc.shm_size</literal>
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Read the sections on this carefully below.
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</para>
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<para>
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Once the server is running, the <literal>apc.php</literal> script that
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is bundled with the extension should be copied somewhere into the docroot and
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viewed with a browser as it provides a detailed analysis of the internal
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workings of APCu. If GD is enabled in PHP, it will even display some
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interesting graphs. If APCu is working, the <literal>Cache full count
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</literal> number (on the left) will display the number of times the cache
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has reached maximum capacity and has had to forcefully clean any entries that
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haven't been accessed in the last <literal>apc.ttl</literal> seconds. This
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number is minimized in a well-configured cache. If the cache is constantly
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being filled, and thusly forcefully freed, the resulting churning will have
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disparaging effects on script performance. The easiest way to minimize this
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number is to allocate more memory for APCu.
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</para>
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<para>
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When APCu is compiled with mmap support (Memory Mapping), it will use only one
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memory segment, unlike when APCu is built with SHM (SysV Shared Memory) support
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that uses multiple memory segments. MMAP does not have a maximum limit like SHM
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does in <literal>/proc/sys/kernel/shmmax</literal>. In general MMAP support is
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recommended because it will reclaim the memory faster when the webserver is
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restarted and all in all reduces memory allocation impact at startup.
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</para>
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<para>
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<table>
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<title>APCu 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><link linkend="ini.apcu.enabled">apc.enabled</link></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><link linkend="ini.apcu.shm-segments">apc.shm_segments</link></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><link linkend="ini.apcu.shm-size">apc.shm_size</link></entry>
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<entry>"32M"</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><link linkend="ini.apcu.entries-hint">apc.entries_hint</link></entry>
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<entry>"4096"</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><link linkend="ini.apcu.ttl">apc.ttl</link></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><link linkend="ini.apcu.gc-ttl">apc.gc_ttl</link></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><link linkend="ini.apcu.mmap-file-mask">apc.mmap_file_mask</link></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><link linkend="ini.apcu.slam-defense">apc.slam_defense</link></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><link linkend="ini.apcu.enable-cli">apc.enable_cli</link></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><link linkend="ini.apcu.use-request-time">apc.use_request_time</link></entry>
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<entry>"0"</entry>
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<entry>PHP_INI_ALL</entry>
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<entry>Prior to APCu 5.1.19, the default was "1".</entry>
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</row>
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<row>
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<entry><link linkend="ini.apcu.serializer">apc.serializer</link></entry>
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<entry>"php"</entry>
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<entry>PHP_INI_SYSTEM</entry>
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<entry>Prior to APCu 5.1.15, the default was "default".</entry>
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</row>
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<row>
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<entry><link linkend="ini.apcu.coredump-unmap">apc.coredump_unmap</link></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><link linkend="ini.apcu.preload-path">apc.preload_path</link></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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</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 xml:id="ini.apcu.enabled">
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<term>
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<parameter>apc.enabled</parameter>
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<type>bool</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 xml:id="ini.apcu.shm-segments">
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<term>
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<parameter>apc.shm_segments</parameter>
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<type>int</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 <literal>apc.shm_size</literal>
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is set as high as the system allows, raising
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this value might prevent APC from exhausting its memory.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="ini.apcu.shm-size">
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<term>
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<parameter>apc.shm_size</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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The size of each shared memory segment given by a shorthand notation as
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described in <link linkend="faq.using.shorthandbytes">this FAQ</link>.
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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 xml:id="ini.apcu.entries-hint">
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<term>
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<parameter>apc.entries_hint</parameter>
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<type>int</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 variables that might be stored.
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Set to zero or omit if not sure.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="ini.apcu.ttl">
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<term>
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<parameter>apc.ttl</parameter>
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<type>int</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 APC's cache could potentially fill up
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with stale entries while newer entries won't be
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cached. In the event of a cache running out of
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available memory, the cache will be completely
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expunged if ttl is equal to 0. Otherwise, if the
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ttl is greater than 0, APC will attempt to remove
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expired entries.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="ini.apcu.gc-ttl">
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<term>
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<parameter>apc.gc_ttl</parameter>
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<type>int</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 xml:id="ini.apcu.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 determining 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 xml:id="ini.apcu.slam-defense">
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<term>
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<parameter>apc.slam_defense</parameter>
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<type>int</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 xml:id="ini.apcu.enable-cli">
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<term>
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<parameter>apc.enable_cli</parameter>
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<type>int</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. Under normal circumstances, it is
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not ideal to create, populate and destroy the APC cache on every
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CLI request, but for various test scenarios it is useful to be
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able to enable APC for the CLI version of PHP easily.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="ini.apcu.serializer">
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<term>
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<parameter>apc.serializer</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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Used to configure APC to use a third party serializer.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="ini.apcu.coredump-unmap">
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<term>
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<parameter>apc.coredump_unmap</parameter>
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<type>bool</type>
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</term>
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<listitem>
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<para>
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Enables APC handling of signals, such as SIGSEGV, that write
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core files when signaled. When these signals are received,
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APC will attempt to unmap the shared memory segment in order
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to exclude it from the core file. This setting may improve
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system stability when fatal signals are received and a large
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APC shared memory segment is configured.
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</para>
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<warning>
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<para>
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This feature is potentially dangerous. Unmapping the shared
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memory segment in a fatal signal handler may cause undefined
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behaviour if a fatal error occurs.
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</para>
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</warning>
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<note>
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<para>
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Although some kernels may provide a facility to ignore various
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types of shared memory when generating a core dump file, these
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implementations may also ignore important shared memory segments
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such as the Apache scoreboard.
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</para>
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</note>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="ini.apcu.preload-path">
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<term>
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<parameter>apc.preload_path</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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Optionally, set a path to the directory that APC will load
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cache data at startup.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry xml:id="ini.apcu.use-request-time">
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<term>
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<parameter>apc.use_request_time</parameter>
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<type>bool</type>
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</term>
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<listitem>
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<para>
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Use the <acronym>SAPI</acronym> request start time for
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<acronym>TTL</acronym>.
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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:"~/.phpdoc/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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