Friday Mar 15, 2013

Using PHP 5.5's New "OPcache" Opcode Cache

Zend have contributed their Zend Optimizer+ opcode cache to PHP - thanks Zend!!! (Update 19 March 2013: the renaming to "Zend OPcache" is complete)

"The Zend OPcache provides faster PHP execution through opcode caching and optimization."

The new OPcache extension can be seen as substitute for the venerable APC cache, the maintenance of which had become an issue. Note: although OPcache is now readily available, there is currently nothing preventing you from using any available (working!) opcode cache in PHP 5.5.

A few minutes ago Dmitry Stogov did the physical merge to the PHP 5.5 source's ext/opcache directory. The current PHP 5.5 snapshot has the code. Future Alpha or Beta (and Production) releases will include it too.

Please test OPcache. It is not a panacea for all performance problems. There are a lot of settings which may need adjusting. Understanding how it works and identifying issues during the stabilization phase of PHP 5.5 release process will greatly help.

To build Zend OPcache for PHP 5.5:

When you configure PHP, add the option --enable-opcache like:

./configure ... --enable-opcache

Then make and make install, as normal. This will build OPcache shared extension. It's not possible to build it statically.

Find the shared library in your installation directory with a command like find /home/cjones/php55 -name opcache.so

Edit php.ini and add the extension with its full path:

zend_extension=/home/cjones/php55/lib/php/extension/debug-non-zts-20121212/opcache.so

Update (25 March 2013): Dmitry merged a PHP 5.5 change so that the full path is not required for zend_extension libraries in the extension_dir directory. You can now simply do zend_extension=opcache.so.

You'll want to enable OPcache too:

opcache.enable=On

The ext/opcache/README is the current source of documentation, and lists all the other php.ini parameters.

Problems can be reported in the Github issue tracker

Update (18 March 2013): In a commit over the weekend, the build option --enable-opcache is On by default. You will still need to update php.ini.

To build Zend OPcache for older versions of PHP:

You should be able to build OPcache with PHP 5.2 onwards

Install it by getting the source from Github. There is also a PECL repository; this is slightly out of date so I recommend using Github. Follow the README instructions to install it.

User-data cache:

The new opcode cache does not include a user-data cache. Joe Watkins recently started the APCu project to extract the user-data cache code from APC. Test this too!

Update 19 March 2013: Xinchen Hui is working on a lockless user-data cache, see https://github.com/laruence/yac and his blog about it here (in Chinese).

About

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I'm a Product Manager in Server Technologies, working on scripting languages and developer-access.
Email: christopher.jones@oracle.com
Twitter: http://twitter.com/ghrd
Book: Free PHP Oracle book
Download: PHP Linux RPMs with the OCI8 extension
Links: OTN PHP Developer Center

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