I came across this Apache configuration:

<IfModule mpm_prefork_module>
    StartServers          16
    MinSpareServers       16
    MaxSpareServers       32
    ServerLimit           400
    MaxClients            400
    MaxRequestsPerChild   10000

<IfModule mpm_worker_module>
    StartServers          4
    MaxClients            1024
    MinSpareThreads       64
    MaxSpareThreads       192
    ThreadsPerChild       64
    MaxRequestsPerChild   0

Currently, only the mpm_prefork_module is installed. But what happens if the mpm_worker_module is installed on the server? This configuration worries me.

This question is similar, but the answer only says how to find the current MPM being used, not what the standard behavior is, or if the behavior is undefined.

  • 1
    From what I remember, when you install one, it disables the other. Could be wrong but that is what I remember.
    – ETL
    Mar 9, 2014 at 0:52

2 Answers 2


It's impossible for both to be used - only one of the MPMs can be in use at a time.

How you configure which is being used depends on how your distribution handles it, but you shouldn't be worried about both at the same time in the same running instance, because that can't happen.


Default when you installed them from binary (rpm, deb, ... or via yum, apt-get, ...), it alway use prefork. If you want to run with worker, need build from source. But worker just best work if you run fcgi php.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .