Two process management modes in PHP-FPM

There are two process management modes of php-fpm. The number of processes of php-fpm can also be divided into dynamic and static according to the settings. One is to directly start a specified number of php-fpm processes without increasing or decreasing it; the other is to start a certain number of php-fpm processes at the beginning, and when the request volume becomes larger, dynamically increase the php-fpm processes. Count to the upper limit, and automatically release idle processes when they are idle. Count to a lower limit.
These two different execution methods can be adjusted according to the actual needs of the server.
Let’s first talk about several parameters involved in this. They are pm, pm.max_children, pm.start_servers, pm.min_spare_servers and pm.max_spare_servers.
pm indicates which method to use. There are two values ​​to choose from, namely static (static) or dynamic (dynamic).
In older versions, dynamic is called apache-like. Please pay attention to the instructions given in the configuration file. The default static processing method of PHP5.3php-fpm will cause the php-cgi process to occupy memory for a long time and cannot be released. This is also one of the reasons for nginx errors. Therefore, the processing method of php-fpm can be changed to apache mode.
The meanings of the following four parameters are: pm.max_children: The number of php-fpm processes opened in static mode.
pm.start_servers: The number of starting php-fpm processes in dynamic mode.
pm.min_spare_servers: The minimum number of php-fpm processes in dynamic mode.
pm.max_spare_servers: The maximum number of php-fpm processes in dynamic mode. If dm is set to static, then only the parameter pm.max_children takes effect. The system will open the set number of php-fpm processes.
If dm is set to dynamic, then the pm.max_children parameter will be invalid and the next three parameters will take effect. The system will start pm.start_servers php-fpm processes when php-fpm starts running, and then dynamically adjust the number of php-fpm processes between pm.min_spare_servers and pm.max_spare_servers according to the needs of the system.
So, which execution method is better for our server? In fact, like Apache, the PHP program we run will more or less have memory leaks after execution.
This is also the reason why a php-fpm process only occupies about 3M of memory at the beginning, and it will increase to 20-30M after running for a period of time. Therefore, the dynamic method will end redundant processes and can recycle and release some memory, so it is recommended to be used on servers or VPS with less memory. The specific maximum amount is obtained based on memory/20M. For example, for a 512M VPS, it is recommended to set pm.max_spare_servers to 20. As for pm.min_spare_servers, it is recommended to set it according to the load of the server. A more suitable value is between 5 and 10.
Then for servers with relatively large memory, setting it to static will improve efficiency. Because frequent switching of the php-fpm process will cause lag, it will be better to turn on the static function if the memory is large enough. Quantity can also be obtained based on memory/30M. For example, a server with 2GB memory can be set to 50; a server with 4GB memory can be set to 100, etc.

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