Sun Java System Web Server 6.1 SP9 Performance Tuning, Sizing, and Scaling Guide

Native Thread Pools (Windows Only)

On Windows, the native thread pool (NativePool) is used internally by the server to execute NSAPI functions that require a native thread for execution. Windows users can edit native thread pool settings using the Server Manager.

Sun Java System Web Server uses NSPR, which is an underlying portability layer providing access to the host OS services. This layer provides abstractions for threads that are not always the same as those for the OS-provided threads. These non-native threads have lower scheduling overhead so their use improves performance. However, these threads are sensitive to blocking calls to the OS, such as I/O calls. To make it easier to write NSAPI extensions that can make use of blocking calls, the server keeps a pool of threads that safely support blocking calls. This usually means it is a native OS thread. During request processing, any NSAPI function that is not marked as being safe for execution on a non-native thread is scheduled for execution on one of the threads in the native thread pool.

If you have written your own NSAPI plugins such as NameTrans, Service, or PathCheck functions, these execute by default on a thread from the native thread pool. If your plugin makes use of the NSAPI functions for I/O exclusively or does not use the NSAPI I/O functions at all, then it can execute on a non-native thread. For this to happen, the function must be loaded with a NativeThread=”no” option, indicating that it does not require a native thread.

To do this, add the following to the "load-modules" Init line in the magnus.conf file:

Init funcs="pcheck_uri_clean_fixed_init"
shlib="C:/Netscape/p186244/P186244.dll" fn="load-modules" 

The NativeThread flag affects all functions in the funcs list, so if you have more than one function in a library, but only some of them use native threads, use separate Init lines.