Prefork (multi-process, each process produces child processes) and worker (multiple processes, each process generates more than one thread)
Prefork works by controlling the process after initially establishing a "startservers" sub-process, creating a process to meet minspareservers settings, waiting one second, continuing to create two, waiting one second, and continuing to create four ... This increases the number of processes created by the number of digits, up to 32 per second, until the value of the Minspareservers setting is met. This is the origin of pre-derivation (prefork). This pattern eliminates the need to generate new processes when the request arrives, reducing overhead to increase performance. Worker is a new MPM in version 2.0 that supports multi-threaded and multi-process hybrid models. Because threads are used for processing, relatively large amounts of requests can be handled, and system resources are less expensive than process-based servers. However, workers also use multiple processes, and each process generates multiple threads to obtain stability based on the process server. This mpm's way of working will be the development trend of Apache 2.0. The current module of Apache can be viewed by command httpd-l, if the worker.c is working in worker mode, if PREFORK.C is working in PREFORK.C mode.
A detailed explanation of Linux Apache prefork and worker principles
