The Alternative PHP Cache install
The Alternative PHP Cache (APC) is a free and open opcode cache for PHP. It was conceived of to provide a free, open, and robust framework for caching and optimizing PHP intermediate code. from http://nl2.php.net/apc
Links:
- http://nl2.php.net/apc
- http://pecl.php.net/package/APC
- Joomla! performance testing "For shared hosts you can best make use of APC or eAccelerator"
Unpack your distribution file. You will have downloaded a file named something like apc_x.y.tar.gz. Unzip this file with a command like# wget http://pecl.php.net/get/APC-3.0.14.tgz
# gunzip apc_x.y.tar.gz
Next you have to untar it with# tar xvf apc_x.y.tar
This will create an apc_x.y directory. cd into this new directory:# cd apc_x.y
phpize is a script that should have been installed with PHP, and is normally located in /usr/local/php/bin assuming you installed PHP in /usr/local/php. (If you do not have the phpize script, you must reinstall PHP and be sure not to disable PEAR.).
Locate phpize:# find / -name phpize
mine is in /etc/alternatives/phpize
yours may be in /usr/local/php/bin/phpize
Run the phpize command:# /usr/local/php/bin/phpize
Its output should resemble this: Configuring for:
PHP Api Version: 20020918
Zend Module Api No: 20020429
Zend Extension Api No: 20021010
phpize should create a configure script in the current directory. If you get errors instead, you might be missing some required development tools, such as autoconf or libtool. You can try downloading the latest versions of those tools and running phpize again.
Run the configure script.
phpize creates a configure script. The only option you need to specify is the location of your php-config script.
find location of php-config# find / -name php-config
then# ./configure --enable-apc --enable-apc-mmap --with-apxs --with-php-config=/etc/alternatives/php-config
php-config should be located in the same directory as phpize.
If you prefer to use mmap instead of the default IPC shared memory support, add --enable-apc-mmap to your configure line.
If you prefer to use sysv IPC semaphores over the safer fcntl() locks, add –enable-sem to your configure line. If you don’t have a problem
with your server segaulting, or any other unnatural accumulation of semaphores on your system, the semaphore based locking is slightly faster.
Compile and install the files.
Simply type: # make install
Installing shared extensions: /usr/lib/php5/extensions/
Suggested Configuration (in your php.ini file)
extension=apc.so
apc.enabled=1
apc.shm_segments=1
apc.shm_size=128
apc.ttl=7200
apc.user_ttl=7200
apc.num_files_hint=1024
apc.mmap_file_mask=/tmp/apc.XXXXXX
apc.enable_cli=1
Although the default APC settings are fine for many installations, serious
users should consider tuning the following parameters:
OPTION DESCRIPTION
—————— ————————————————–
apc.enabled This 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 zend_extension
line can just be commented-out).
(Default: 1)
apc.shm_segments The number of shared memory segments to allocate
for the compiler cache. If APC is running out of
shared memory but you have already set
apc.shm_size as high as your system allows, you
can try raising this value. Setting this to a
value other than 1 has no effect in mmap mode
since mmap’ed shm segments don’t have size limits.
(Default: 1)
apc.shm_size The size of each shared memory segment in MB.
By default, some systems (including most BSD
variants) have very low limits on the size of a
shared memory segment.
(Default: 30)
apc.optimization This option has been deprecated.
(Default: 0)
apc.num_files_hint A "hint" about the number of distinct source files
that will be included or requested on your web
server. Set to zero or omit if you’re not sure;
this setting is mainly useful for sites that have
many thousands of source files.
(Default: 1000)
apc.user_entries_hint Just like num_files_hint, a "hint" about the number
of distinct user cache variables to store.
Set to zero or omit if you’re not sure;
(Default: 4096)
apc.ttl 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 your cache could potentially fill up
with stale entries while newer entries won’t be
cached.
(Default: 0)
apc.user_ttl The number of seconds a user 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 your cache could potentially fill up
with stale entries while newer entries won’t be
cached.
(Default: 0)
apc.gc_ttl The number of seconds that a cache entry may
remain on the garbage-collection list. This value
provides a failsafe 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.
(Default: 3600)
apc.cache_by_default On by default, but can be set to off and used in
conjunction with positive apc.filters so that files
are only cached if matched by a positive filter.
(Default: On)
apc.filters A comma-separated list of POSIX extended regular
expressions. If any pattern matches the source
filename, the file will not be cached. Note that
the filename used for matching is the one passed
to include/require, not the absolute path. If the
first character of the expression is a + then the
expression will be additive in the sense that any
files matched by the expression will be cached, and
if the first character is a – then anything matched
will not be cached. The – case is the default, so
it can be left off.
(Default: "")
apc.mmap_file_mask If compiled with MMAP support by using –enable-mmap
this is the mktemp-style file_mask to pass to the
mmap module for determing 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 /tmp/apc.XXXXXX (exactly 6 X’s).
To use POSIX-style shm_open/mmap put a ".shm"
somewhere in your mask. eg. "/apc.shm.XXXXXX"
You can also set it to "/dev/zero" to use your
kernel’s /dev/zero interface to anonymous mmap’ed
memory. Leaving it undefined will force an
anonymous mmap.
(Default: "")
apc.slam_defense ** DEPRECATED – Use apc.write_lock instead **
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 this to 75 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 0 disables this
feature.
(Default: 0)
apc.file_update_protection
When you modify a file on a live web server you really
should do so in an atomic manner. That is, write to a
temporary file and rename (mv) the file into its permanent
position when it is ready. Many text editors, cp, tar and
other such programs don’t do this. This means that there
is a chance that a file is accessed (and cached) while it
is still being written to. This file_update_protection
setting puts a delay on caching brand new files. The
default is 2 seconds which means that if the modification
timestamp (mtime) on a file shows that it is less than 2
seconds old when it is accessed, it will not be cached.
The unfortunate person who accessed this half-written file
will still see weirdness, but at least it won’t persist.
If you are certain you always atomically update your files
by using something like rsync which does this correctly, you
can turn this protection off by setting it to 0. If you
have a system that is flooded with io causing some update
procedure to take longer than 2 seconds, you may want to
increase this a bit.
(Default: 2)
apc.enable_cli Mostly for testing and debugging. Setting this enables APC
for the CLI version of PHP. Normally you wouldn’t want to
create, populate and tear down the APC cache on every CLI
request, but for various test scenarios it is handy to be
able to enable APC for the CLI version of APC easily.
(Default: 0)
apc.max_file_size Prevents large files from being cached.
(Default: 1M)
apc.stat Whether to stat the main script file and the fullpath
includes. If you turn this off you will need to restart
apc.write_lock On busy servers when you first start up the server, or when
many files are modified, you can end up with all your processes
trying to compile and cache the same files. With write_lock
enabled, only one process at a time will try to compile an
uncached script while the other processes will run uncached
instead of sitting around waiting on a lock.
(Default: 1)
apc.report_autofilter Logs any scripts that were automatically excluded from being
cached due to early/late binding issues.
(Default: 0)
apc.rfc1867 RFC1867 File Upload Progress hook handler is only available
if you compiled APC against PHP 5.2.0 or later. When enabled
any file uploads which includes a field called
APC_UPLOAD_PROGRESS before the file field in an upload form
will cause APC to automatically create an upload_<key>
user cache entry where <key> is the value of the
APC_UPLOAD_PROGRESS form entry.
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.
(Default: 0)
apc.localcache This enables a lock-free local process shadow-cache which
reduces lock contention when the cache is being written to.
(Default: 0)
apc.localcache.size The size of the local process shadow-cache, should be set to
a sufficently large value, approximately half of num_files_hint.
(Default: 512)
apc.include_once_override
Optimize include_once and require_once calls and avoid the
expensive system calls used.
(Default: 0)
