Apache HTTP Server /etc/apache2/conf.d/mpm.conf

#
# Server-Pool Management (MPM specific)
# 

#
# PidFile: The file in which the server should record its process
# identification number when it starts.
#
# Note that this is the default PidFile for most MPMs.
#
<IfModule !mpm_netware_module>
    PidFile "/run/apache2/httpd.pid"
</IfModule>

#
# Only one of the below sections will be relevant on your
# installed httpd.  Use "apachectl -l" to find out the
# active mpm.
#

# prefork MPM
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# MaxRequestWorkers: maximum number of server processes allowed to start
# MaxConnectionsPerChild: maximum number of connections a server process serves
#                         before terminating
<IfModule mpm_prefork_module>
    StartServers             5
    MinSpareServers          5
    MaxSpareServers         10
    MaxRequestWorkers      250
    MaxConnectionsPerChild   0
</IfModule>

# worker MPM
# StartServers: initial number of server processes to start
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestWorkers: maximum number of worker threads
# MaxConnectionsPerChild: maximum number of connections a server process serves
#                         before terminating
<IfModule mpm_worker_module>
    StartServers             3
    MinSpareThreads         75
    MaxSpareThreads        250 
    ThreadsPerChild         25
    MaxRequestWorkers      400
    MaxConnectionsPerChild   0
</IfModule>

# event MPM
# StartServers: initial number of server processes to start
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestWorkers: maximum number of worker threads
# MaxConnectionsPerChild: maximum number of connections a server process serves
#                         before terminating
<IfModule mpm_event_module>
    StartServers             3
    MinSpareThreads         75
    MaxSpareThreads        250
    ThreadsPerChild         25
    MaxRequestWorkers      400
    MaxConnectionsPerChild   0
</IfModule>

# NetWare MPM
# ThreadStackSize: Stack size allocated for each worker thread
# StartThreads: Number of worker threads launched at server startup
# MinSpareThreads: Minimum number of idle threads, to handle request spikes
# MaxSpareThreads: Maximum number of idle threads
# MaxThreads: Maximum number of worker threads alive at the same time
# MaxConnectionsPerChild: Maximum  number of connections a thread serves. It
#                         is recommended that the default value of 0 be set
#                         for this directive on NetWare.  This will allow the
#                         thread to continue to service requests indefinitely.
<IfModule mpm_netware_module>
    ThreadStackSize      65536
    StartThreads           250
    MinSpareThreads         25
    MaxSpareThreads        250
    MaxThreads            1000
    MaxConnectionsPerChild   0
</IfModule>

# OS/2 MPM
# StartServers: Number of server processes to maintain
# MinSpareThreads: Minimum number of idle threads per process, 
#                  to handle request spikes
# MaxSpareThreads: Maximum number of idle threads per process
# MaxConnectionsPerChild: Maximum number of connections per server process
<IfModule mpm_mpmt_os2_module>
    StartServers             2
    MinSpareThreads          5
    MaxSpareThreads         10
    MaxConnectionsPerChild   0
</IfModule>

# WinNT MPM
# ThreadsPerChild: constant number of worker threads in the server process
# MaxConnectionsPerChild: maximum number of connections a server process serves
<IfModule mpm_winnt_module>
    ThreadsPerChild        150
    MaxConnectionsPerChild   0
</IfModule>

# The maximum number of free Kbytes that every allocator is allowed
# to hold without calling free(). In threaded MPMs, every thread has its own
# allocator. When not set, or when set to zero, the threshold will be set to
# unlimited.
<IfModule !mpm_netware_module>
    MaxMemFree            2048
</IfModule>
<IfModule mpm_netware_module>
    MaxMemFree             100
</IfModule>