Measuring Performance Bottlenecks

Measurement is the most crucial aspect of building high-performance systems. You can't change what you don't measure because you won't know what effect your change has had, if any. Without measuring your application, you won't know whether it's performing well.

If you only go by when your software feels slow, then you have left it too late. You are reactively fixing a problem rather than proactively avoiding one. You must measure to achieve good performance, even though it's the feel that matters to a user.

Some books leave measurement, analysis, and profiling until the end. Yet, this is the first thing that should be considered. It's common to fix the wrong problem and optimize areas that do not have performance difficulties.

In this chapter, we will cover the following topics:

• Structured Query Language database profiling
• Web application profiling
• HTTP monitoring
• Network monitoring
• Scientific method and repeatability

This chapter will show you how to check for performance issues and where they are occurring. We will describe the tools that can give you this information and demonstrate how to use them effectively and correctly. We'll also show you how to repeat your experiments consistently so that you can tell whether you have fixed a problem once you've identified it.

We will cover measurement again toward the end of the book, but there, we'll focus on continuous automated monitoring to avoid regressions. This chapter will focus more on manual testing to identify potential performance problems during development and debugging.