Enable PHP Opcode Cache for LiteSpeed

Since PHP 5.5, Zend Opcode Cache has been included in the PHP main package distribution and can be easily installed through yum or apt-get. For PHP 5.4 and lower, you can use APC cache. APC cache already includes PHP opcode cache and user cache. To use user/variable cache for PHP 5.5 and up with Zend Opcode cache only, you may also add apcu.

Xcache may also be used with PHP up to version 5.6, but not 7.0.

Opcode cache can be easily installed through yum or apt-get. To see if it has been enabled, check the corresponding phpinfo page. If you use the PHP non-EXEC mode you may be finished at this point, however when using PHP SuEXEC mode for shared hosting environments such as cPanel or Plesk, you also have to choose the right LSPHP SuEXEC mode.

For shared hosting environments such as cPanel or Plesk, you should use the PHP SuEXEC mode. LSWS Web Admin → Server → General → Using Apache Configuration File → PHP suEXEC → Yes. When you check a user's phpinfo page, it may show that Zend Opcode Cache is installed and enabled. However there are three PHP SuEXEC modes for LiteSpeed: suEXEC Worker Mode, suEXEC Daemon Mode and suEXEC ProcessGroup Mode.

You may follow this wiki to check which SuEXEC mode you are using. suEXEC Daemon Mode and suEXEC ProcessGroup Mode support opcode cache while the default suEXEC Worker Mode does not. If using opcode cache, you will need to change to suEXEC Daemon Mode or suEXEC ProcessGroup Mode.

To set up suEXEC Daemon mode, you need only adjust your server-level LSPHP external application settings in the WebAdmin console > Configuration > External App > your LSPHP external application:

Set Start By Server to "Yes".
Set Run On Start Up to "suEXEC Daemon".

To set up ProcessGroup, you need to place the directive LSPHP_ProcessGroup in an httpd.conf file. This can be done at the server or virtual host level. If done at the server level, all virtual hosts will use ProcessGroup. If done at the virtual host level, only that virtual host will use ProcessGroup.

Example configuration:

<IfModule LiteSpeed>
LSPHP_ProcessGroup on
LSPHP_Workers 15
</IfModule>

Process Group Mode is similar to Apache php-fpm mode. The difference is: with Apache, the parent process of php-fpm is not controlled by Apache, and it keeps running; with LiteSpeed, LiteSpeed uses LSAPI, and the PHP will exit if idle for a while (in a shared hosting environment and set at "Max Idle time"). For LSWS 5.2.8 and lower versions, PHP processes will stop when LSWS restarts, and the opcode cache will be reset. Starting from LSWS 5.3RC2 and above, LSPHP will run in detached mode and an LSWS restart won't stop PHP processes. The LSPHP parent will just follow the timeout where "Max Idle time" is set.

Please keep in mind that keep idle PHP process running longer will occupy server resources and there is a risk to overload the server if there is not enough resources.

For LSWS 2CPU and above licenses, you have an option to configure LSWS to use multi CPU cores. For LSWS 5.2.x and below, When a domain is served by multi-CPU cores, Opcode cache cannot be shared between CPU cores. So, when you test a phpinfo.php page, you might see cache hits like the following upon refresh:

http://example.com/phpinfo.php
  
505
0
1
506
507
1
2

As of LiteSpeed Web Server v5.3RC2 and above, LSWS can share opcache between Multi CPU processes.

Non-shared hosting environments should use PHP non-exec mode. (LSWS Web Admin > Server > General > Using Apache Configuration File > PHP suEXEC = No). LSPHP just runs in workgroup mode as the “nobody” user by default. For this situation, as long as you see opcode cache in the phpinfo page, opcode cache has already been enabled.

More details about PHP SuEXEC or non-SuEXEC here.