Apache Cookbook, 2nd Edition

11.10. Tuning Thread Creation

Problem

You’re using Apache 2.0 with one of the threaded MPMs, and you want to optimize the settings for the number of threads.

Solution

Will vary from server to server.

Discussion

The various threaded MPMs on Apache 2.0 handle thread creation somewhat differently. In Apache 1.3, the Windows and Netware versions are threaded, whereas the Unixish version is not. Tuning the thread creation values will vary from one of these versions to another.

Setting the number of threads on single-child MPMs

On MPMs that run Apache with a single threaded child process, such as the Windows MPM (mpm_winnt) and the Windows and Netware versions of Apache 1.3, there are a fixed number of threads in the child process. This number is controlled by the ThreadsPerChild directive and must be large enough to handle the peak traffic of the site on any given day. There really is no performance tuning that can be done here, as this number is fixed throughout the lifetime of the Apache process.

Number of threads when using the worker MPM

The worker MPM has a fixed number of threads per child process but has a variable number of child processes so that increased server load can be absorbed. A typical configuration might look like the following:

StartServers 2
MaxClients 150
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
ServerLimit 16

The MinSpareThreads and MaxSpareThreads directives control the size of the idle pool of threads, so that incoming clients will always have an idle thread ...