Tomcat: The Definitive Guide, 2nd Edition

External Tuning

Once you've got an idea how your application and Tomcat instance respond to load, you can begin some performance tuning. There are two basic categories of tuning detailed here:

External tuning

Tuning that involves non-Tomcat components, such as the operating system that Tomcat runs on and the Java virtual machine running Tomcat.

Internal tuning

Tuning that deals with Tomcat itself, ranging from changing settings in configuration files to modifying the Tomcat source code. Modifications to your web application also fall into this category.

In this section, we detail the most common areas of external tuning, and then move on to internal tuning in the next section.

JVM Performance

Tomcat doesn't run directly on a computer; there is a JVM and an operating system between it and the underlying hardware. There are relatively few complete and fully compatible Java virtual machines to choose from for any given operating system and architecture combination, so most people will probably stick with Sun's or their own operating system vendor's implementation.

If your goal is to run the fastest Java runtime and squeeze the most performance out of your webapp, you should benchmark Tomcat and your webapp on each of the Java VMs that are available for your hardware and operating system combination. Do not assume that the Sun Java VM is going to be the fastest because that is often not the case (at least in our experience). You should try other brands and even different major version numbers ...