Sun Java System Web Server 7.0 Update 7 Performance Tuning, Sizing, and Scaling Guide

Too Few Threads

The server does not allow the number of active threads to exceed the thread limit value. If the number of simultaneous requests reaches that limit, the server stops servicing new connections until the old connections are freed up. This can lead to increased response time.

In Web Server, the server’s default maximum threads setting is greater of 128 or the number of processors in the system. If you want your server to process more requests concurrently, you need to increase the maximum number of threads.

The symptom of a server with too few threads is a long response time. Making a request from a browser establishes a connection fairly quickly to the server, but if there are too few threads on the server it can take a long time before the response comes back to the client.

The best way to tell if your server is being throttled by too few threads is to see if the number of active sessions is close to, or equal to, the maximum number of threads. To do this, see Session Creation and Thread Information.