Apache Reference Manual (8)

MaxRequestsPerChild directive
Syntax: MaxRequestsPerChild number
Default: MaxRequestsPerChild 0
Context: server config
Status: core
The MaxRequestsPerChild directive sets the limit on the number of requests that an individual child server process will handle. After MaxRequestsPerChild requests, the child process will die. If MaxRequestsPerChild is 0, then the process will never expire.
Setting MaxRequestsPerChild to a non-zero limit has two beneficial effects:
it limits the amount of memory that process can consume by (accidental) memory leakage;
by giving processes a finite lifetime, it helps reduce the number of processes when the server load reduces.
This directive has no effect on Win32.
NOTE: For KeepAlive requests, only the first request is counted towards this limit. In effect, it changes the behavior to limit the number of connections per child.
--------------------------------------------------------------------------------
MaxSpareServers directive
Syntax: MaxSpareServers number
Default: MaxSpareServers 10
Context: server config
Status: core
The MaxSpareServers directive sets the desired maximum number of idle child server processes. An idle process is one which is not handling a request. If there are more than MaxSpareServers idle, then the parent process will kill off the excess processes.
Tuning of this parameter should only be necessary on very busy sites. Setting this parameter to a large number is almost always a bad idea.
This directive has no effect when used with the Apache Web server on a Microsoft Windows platform.
See also MinSpareServers and StartServers.
--------------------------------------------------------------------------------
MinSpareServers directive
Syntax: MinSpareServers number
Default: MinSpareServers 5
Context: server config
Status: core
The MinSpareServers directive sets the desired minimum number of idle child server processes. An idle process is one which is not handling a request. If there are fewer than MinSpareServers idle, then the parent process creates new children at a maximum rate of 1 per second.