mod_mpm_prefork vs mod_mpm_worker

The Apache Multi-Processing Modules (MPMs) mod_mpm_prefork and mod_mpm_worker handle incoming connections differently, impacting performance and resource usage. mod_mpm_prefork uses a separate process for each connection, offering stability but potentially consuming more resources. mod_mpm_worker uses multiple threads within each process, improving performance and resource efficiency, especially under high traffic, but can be less stable with non-thread-safe modules. 

Here’s a more detailed breakdown:

mod_mpm_prefork:

• Process-based: Each incoming connection is handled by a new, separate process. 
• Stability: Isolation of processes makes it more stable, especially when dealing with non-thread-safe modules (like older PHP versions). 
• Resource Consumption: Each process consumes more memory and resources compared to threads. 
• Performance: Generally slower than mod_mpm_worker in high-traffic situations due to the overhead of creating new processes. 
• Use Cases: Best for low to medium traffic sites, sites that require strict isolation of requests, or when using non-thread-safe modules. 

mod_mpm_worker:

• Hybrid (Process and Thread):Uses multiple threads within each process to handle requests, offering a balance between performance and resource usage.
• Performance:More efficient in handling a large number of concurrent connections, leading to faster page load times.
• Resource Usage:More resource-efficient than mod_mpm_prefork due to fewer processes and the use of threads.
• Stability:More susceptible to issues if using non-thread-safe modules, as threads share the same process space.
• Use Cases:Ideal for high-traffic websites and applications that require high performance and can utilize thread-safe modules. 

In essence: 

• If you need maximum stability and are using non-thread-safe modules, mod_mpm_prefork is a safer choice, even if it means sacrificing some performance. 
• If you need high performance and can use thread-safe modules, mod_mpm_worker is the preferred option, offering better resource management and faster response times. 

How to check which MPM is in use:

You can check which MPM is currently active on your Apache server using the following command: 

Code

apache2ctl -l