RHEL 6 Deployment - 11.3.3. Common Multi-Processing Module Directives

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11.3.3. Common Multi-Processing Module Directives

The Multi-Processing Module (MPM) directives allow you to customize the behavior of a particular MPM specific server-pool. Since its characteristics differ depending on which MPM is used, the directives are embeded in IfModule. By default, the server-pool is defined for both the prefork and worker MPMs.

The following MPM directives are commonly used in /etc/httpd/conf/httpd.conf:

MaxClients

The MaxClients directive allows you to specify the maximum number of simultaneously connected clients to process at one time. It takes the following form:

MaxClients number

A high number can improve the performance of the server, although it is not recommended to exceed 256 when using the prefork MPM.

Example 11.71. Using the `MaxClients` directive

MaxClients 256

MaxRequestsPerChild

The MaxRequestsPerChild directive allows you to specify the maximum number of request a child process can serve before it dies. It takes the following form:

MaxRequestsPerChild number

Setting the number to 0 allows unlimited number of requests.

The MaxRequestsPerChild directive is used to prevent long-lived processes from causing memory leaks.

Example 11.72. Using the `MaxRequestsPerChild` directive

MaxRequestsPerChild 4000

MaxSpareServers

The MaxSpareServers directive allows you to specify the maximum number of spare child processes. It takes the following form:

MaxSpareServers number

This directive is used by the prefork MPM only.

Example 11.73. Using the `MaxSpareServers` directive

MaxSpareServers 20

MaxSpareThreads

The MaxSpareThreads directive allows you to specify the maximum number of spare server threads. It takes the following form:

MaxSpareThreads number

The number must be greater than or equal to the sum of MinSpareThreads and ThreadsPerChild. This directive is used by the worker MPM only.

Example 11.74. Using the `MaxSpareThreads` directive

MaxSpareThreads 75

MinSpareServers

The MinSpareServers directive allows you to specify the minimum number of spare child processes. It takes the following form:

MinSpareServers number

Note that a high number can create a heavy processing load on the server. This directive is used by the prefork MPM only.

Example 11.75. Using the `MinSpareServers` directive

MinSpareServers 5

MinSpareThreads

The MinSpareThreads directive allows you to specify the minimum number of spare server threads. It takes the following form:

MinSpareThreads number

This directive is used by the worker MPM only.

Example 11.76. Using the `MinSpareThreads` directive

MinSpareThreads 75

StartServers

The StartServers directive allows you to specify the number of child processes to create when the service is started. It takes the following form:

StartServers number

Since the child processes are dynamically created and terminated according to the current traffic load, it is usually not necessary to change this value.

Example 11.77. Using the `StartServers` directive

StartServers 8

ThreadsPerChild

The ThreadsPerChild directive allows you to specify the number of threads a child process can create. It takes the following form:

ThreadsPerChild number

This directive is used by the worker MPM only.

Example 11.78. Using the `ThreadsPerChild` directive

ThreadsPerChild 25

11.3.3. Common Multi-Processing Module Directives

Example 11.71. Using the MaxClients directive

Example 11.72. Using the MaxRequestsPerChild directive

Example 11.73. Using the MaxSpareServers directive

Example 11.74. Using the MaxSpareThreads directive

Example 11.75. Using the MinSpareServers directive

Example 11.76. Using the MinSpareThreads directive

Example 11.77. Using the StartServers directive

Example 11.78. Using the ThreadsPerChild directive