Apache Tuning: Is it normal for lots of Apache services to clog memory?

Do you use mod mpm worker?

@Rhodesia --

This is normal if you use mpm-prefork. If you use mpm-event or mpm-worker, the number of processes will be reduced significantly because each process will service requests using multiple threads. This can be more efficient if you have a large workload and a multi-core CPU.

These processes don't "clog memory". Processes have a unique structure…what you are seeing basically only represents the data part of apache2(8). Code is only loaded once (since code is read-only, it can be shared among multiple processes). Linux, in general, has pretty efficient process-management. My Roku Streaming Stick (about the size of a USB stick), my daughter's Android phone & my Raspberry-Pi-like SBC all run (custom distros of) Linux.

The kernel also has processes. These are enclosed in [] in a ps -ef listing. For example, on my Linode I have:

root        14     2  0 Apr11 ?        00:00:00 [cpuhp/0]
root        15     2  0 Apr11 ?        00:00:00 [cpuhp/1]

which are the "CPU hotplug" processes that facilitate scheduling of threads/processes in a multi-CPU system.

Switching to mpm-event or mpm-worker is easy but it has impacts on how you configure PHP.

-- sw