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<h2 class="title">Runtime Configuration</h2>
<p class="simpara">
The behaviour of these functions is affected by settings in <var class="filename">php.ini</var>.
</p>
<p class="para">
Although the default APCu settings are fine for many installations, serious
users should consider tuning the following parameters.
</p>
<p class="para">
There is one decision to be made configuring APCu.
How much memory is going to be allocated to APCu.
The ini directive that controls this is <em>apc.shm_size</em>
Read the sections on this carefully below.
</p>
<p class="para">
Once the server is running, the <em>apc.php</em> script that
is bundled with the extension should be copied somewhere into the docroot and
viewed with a browser as it provides a detailed analysis of the internal
workings of APCu. If GD is enabled in PHP, it will even display some
interesting graphs. If APCu is working, the <em>Cache full count
</em> number (on the left) will display the number of times the cache
has reached maximum capacity and has had to forcefully clean any entries that
haven't been accessed in the last <em>apc.ttl</em> seconds. This
number is minimized in a well-configured cache. If the cache is constantly
being filled, and thusly forcefully freed, the resulting churning will have
disparaging effects on script performance. The easiest way to minimize this
number is to allocate more memory for APCu.
</p>
<p class="para">
When APCu is compiled with mmap support (Memory Mapping), it will use only one
memory segment, unlike when APCu is built with SHM (SysV Shared Memory) support
that uses multiple memory segments. MMAP does not have a maximum limit like SHM
does in <em>/proc/sys/kernel/shmmax</em>. In general MMAP support is
recommeded because it will reclaim the memory faster when the webserver is
restarted and all in all reduces memory allocation impact at startup.
</p>
<p class="para">
<table class="doctable table">
<caption><strong>APCu configuration options</strong></caption>
<thead>
<tr>
<th>Name</th>
<th>Default</th>
<th>Changeable</th>
<th>Changelog</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td><a href="apcu.configuration.html#ini.apcu.enabled" class="link">apc.enabled</a></td>
<td>"1"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.shm-segments" class="link">apc.shm_segments</a></td>
<td>"1"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.shm-size" class="link">apc.shm_size</a></td>
<td>"32M"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.entries-hint" class="link">apc.entries_hint</a></td>
<td>"4096"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.ttl" class="link">apc.ttl</a></td>
<td>"0"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.gc-ttl" class="link">apc.gc_ttl</a></td>
<td>"3600"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.mmap-file-mask" class="link">apc.mmap_file_mask</a></td>
<td>NULL</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.slam-defense" class="link">apc.slam_defense</a></td>
<td>"1"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.enable-cli" class="link">apc.enable_cli</a></td>
<td>"0"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.use-request-time" class="link">apc.use_request_time</a></td>
<td>"1"</td>
<td>PHP_INI_ALL</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.serializer" class="link">apc.serializer</a></td>
<td>"default"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.rfc1867" class="link">apc.rfc1867</a></td>
<td>"0"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.rfc1867-prefix" class="link">apc.rfc1867_prefix</a></td>
<td>"upload_"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.rfc1867-name" class="link">apc.rfc1867_name</a></td>
<td>"APC_UPLOAD_PROGRESS"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.rfc1867-freq" class="link">apc.rfc1867_freq</a></td>
<td>"0"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.rfc1867-ttl" class="link">apc.rfc1867_ttl</a></td>
<td>"3600"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.coredump-unmap" class="link">apc.coredump_unmap</a></td>
<td>"0"</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
<tr>
<td><a href="apcu.configuration.html#ini.apcu.preload-path" class="link">apc.preload_path</a></td>
<td>NULL</td>
<td>PHP_INI_SYSTEM</td>
<td class="empty"> </td>
</tr>
</tbody>
</table>
For further details and definitions of the
PHP_INI_* modes, see the <a href="configuration.changes.modes.html" class="xref">Where a configuration setting may be set</a>.
</p>
<p class="para">Here's a short explanation of
the configuration directives.</p>
<p class="para">
<dl>
<dt id="ini.apcu.enabled">
<code class="parameter">apc.enabled</code>
<span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span>
</dt>
<dd>
<p class="para">
<em>apc.enabled</em> can be set to 0 to disable APC. This is
primarily useful when APC is statically compiled
into PHP, since there is no other way to disable
it (when compiled as a DSO, the <em>extension</em>
line in <em>php.ini</em> can just be commented-out).
</p>
</dd>
<dt id="ini.apcu.shm-segments">
<code class="parameter">apc.shm_segments</code>
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
</dt>
<dd>
<p class="para">
The number of shared memory segments to allocate
for the compiler cache. If APC is running out of
shared memory but <em>apc.shm_size</em>
is set as high as the system allows, raising
this value might prevent APC from exhausting its memory.
</p>
</dd>
<dt id="ini.apcu.shm-size">
<code class="parameter">apc.shm_size</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<p class="para">
The size of each shared memory segment given by a shorthand notation as
described in <a href="faq.using.html#faq.using.shorthandbytes" class="link">this FAQ</a>.
By default, some systems (including most BSD
variants) have very low limits on the size of a
shared memory segment.
</p>
</dd>
<dt id="ini.apcu.entries-hint">
<code class="parameter">apc.entries_hint</code>
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
</dt>
<dd>
<p class="para">
A "hint" about the number of distinct variables that might be stored.
Set to zero or omit if not sure.
</p>
</dd>
<dt id="ini.apcu.ttl">
<code class="parameter">apc.ttl</code>
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
</dt>
<dd>
<p class="para">
The number of seconds a cache entry is allowed to
idle in a slot in case this cache entry slot is
needed by another entry. Leaving this at zero
means that APC's cache could potentially fill up
with stale entries while newer entries won't be
cached. In the event of a cache running out of
available memory, the cache will be completely
expunged if ttl is equal to 0. Otherwise, if the
ttl is greater than 0, APC will attempt to remove
expired entries.
</p>
</dd>
<dt id="ini.apcu.gc-ttl">
<code class="parameter">apc.gc_ttl</code>
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
</dt>
<dd>
<p class="para">
The number of seconds that a cache entry may
remain on the garbage-collection list. This value
provides a fail-safe in the event that a server
process dies while executing a cached source file;
if that source file is modified, the memory
allocated for the old version will not be
reclaimed until this TTL reached. Set to zero to
disable this feature.
</p>
</dd>
<dt id="ini.apcu.mmap-file-mask">
<code class="parameter">apc.mmap_file_mask</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<p class="para">
If compiled with MMAP support by using <em>--enable-mmap</em>
this is the mktemp-style file_mask to pass to the
mmap module for determining whether your mmap'ed memory
region is going to be file-backed or shared memory
backed. For straight file-backed mmap, set it to
something like <em>/tmp/apc.XXXXXX</em>
(exactly 6 <em>X</em>s).
To use POSIX-style shm_open/mmap put a <em>.shm</em>
somewhere in your mask. e.g. <em>/apc.shm.XXXXXX</em>
You can also set it to <em>/dev/zero</em> to use your
kernel's <em>/dev/zero</em> interface to anonymous mmap'ed
memory. Leaving it undefined will force an anonymous mmap.
</p>
</dd>
<dt id="ini.apcu.slam-defense">
<code class="parameter">apc.slam_defense</code>
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
</dt>
<dd>
<p class="para">
On very busy servers whenever you start the server or
modify files you can create a race of many processes
all trying to cache the same file at the same time.
This option sets the percentage of processes that will
skip trying to cache an uncached file. Or think of it
as the probability of a single process to skip caching.
For example, setting <em>apc.slam_defense</em>
to <em>75</em> would mean that there is
a 75% chance that the process will not cache an uncached
file. So, the higher the setting the greater the defense
against cache slams. Setting this to <em>0</em>
disables this feature.
</p>
</dd>
<dt id="ini.apcu.enable-cli">
<code class="parameter">apc.enable_cli</code>
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
</dt>
<dd>
<p class="para">
Mostly for testing and debugging. Setting this enables APC
for the CLI version of PHP. Under normal circumstances, it is
not ideal to create, populate and destroy the APC cache on every
CLI request, but for various test scenarios it is useful to be
able to enable APC for the CLI version of PHP easily.
</p>
</dd>
<dt id="ini.apcu.serializer">
<code class="parameter">apc.serializer</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<p class="para">
Used to configure APC to use a third party serializer.
</p>
</dd>
<dt id="ini.apcu.rfc1867">
<code class="parameter">apc.rfc1867</code>
<span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span>
</dt>
<dd>
<p class="para">
RFC1867 File Upload Progress hook handler is only available if APC
was compiled against PHP 5.2.0 or later. When enabled, any file uploads
which includes a field called <em>APC_UPLOAD_PROGRESS</em>
before the file field in an upload form will cause APC to automatically
create an upload_<em class="emphasis">key</em> user cache entry where
<em class="emphasis">key</em> is the value of the
<em>APC_UPLOAD_PROGRESS</em> form entry.
</p>
<p class="para">
Note that the hidden field specified by
<em>APC_UPLOAD_PROGRESS</em> must come before the file field,
otherwise the upload progress will not work correctly.
</p>
<p class="para">
Note that the file upload tracking is not threadsafe at this point, so
new uploads that happen while a previous one is still going will disable
the tracking for the previous.
</p>
<p class="para">
Note that the <em>rate</em> is only available once all file
transfers are completed.
</p>
<p class="para">
<div class="example" id="example-446">
<p><strong>Example #1 An apc.rfc1867 example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">apcu_fetch</span><span style="color: #007700">(</span><span style="color: #DD0000">"upload_</span><span style="color: #0000BB">$_POST</span><span style="color: #007700">[</span><span style="color: #0000BB">APC_UPLOAD_PROGRESS</span><span style="color: #007700">]</span><span style="color: #DD0000">"</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[total] => 1142543
[current] => 1142543
[rate] => 1828068.8
[filename] => test
[name] => file
[temp_filename] => /tmp/php8F
[cancel_upload] => 0
[done] => 1
)
</pre></div>
</div>
</div>
</p>
</dd>
<dt id="ini.apcu.rfc1867-prefix">
<code class="parameter">apc.rfc1867_prefix</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<p class="para">
Key prefix to use for the user cache entry generated by rfc1867 upload
progress functionality.
</p>
</dd>
<dt id="ini.apcu.rfc1867-name">
<code class="parameter">apc.rfc1867_name</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<p class="para">
Specify the hidden form entry name that activates APC upload progress
and specifies the user cache key suffix.
</p>
</dd>
<dt id="ini.apcu.rfc1867-freq">
<code class="parameter">apc.rfc1867_freq</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<p class="para">
The frequency that updates should be made to the user cache entry for
upload progress. This can take the form of a percentage of the total
file size or a size in bytes optionally suffixed with
<em>"k"</em>, <em>"m"</em>, or <em>"g"</em>
for kilobytes, megabytes, or gigabytes respectively (case insensitive).
A setting of 0 updates as often as possible, which may cause slower
uploads.
</p>
</dd>
<dt id="ini.apcu.rfc1867-ttl">
<code class="parameter">apc.rfc1867_ttl</code>
<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>
</dt>
<dd>
<p class="para">
<acronym>TTL</acronym> for rfc1867 entries.
</p>
</dd>
<dt id="ini.apcu.coredump-unmap">
<code class="parameter">apc.coredump_unmap</code>
<span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span>
</dt>
<dd>
<p class="para">
Enables APC handling of signals, such as SIGSEGV, that write
core files when signaled. When these signals are received,
APC will attempt to unmap the shared memory segment in order
to exclude it from the core file. This setting may improve
system stability when fatal signals are received and a large
APC shared memory segment is configured.
</p>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
This feature is potentially dangerous. Unmapping the shared
memory segment in a fatal signal handler may cause undefined
behaviour if a fatal error occurs.
</p>
</div>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Although some kernels may provide a facility to ignore various
types of shared memory when generating a core dump file, these
implementations may also ignore important shared memory segments
such as the Apache scoreboard.
</p>
</p></blockquote>
</dd>
<dt id="ini.apcu.preload-path">
<code class="parameter">apc.preload_path</code>
<span class="type"><a href="language.types.string.html" class="type string">string</a></span>
</dt>
<dd>
<p class="para">
Optionally, set a path to the directory that APC will load
cache data at startup.
</p>
</dd>
<dt id="ini.apcu.use-request-time">
<code class="parameter">apc.use_request_time</code>
<span class="type"><a href="language.types.boolean.html" class="type bool">bool</a></span>
</dt>
<dd>
<p class="para">
Use the <acronym title="Server Application Programming Interface">SAPI</acronym> request start time for
<acronym>TTL</acronym>.
</p>
</dd>
</dl>
</p>
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