3. System View

Now that we’ve introduced you to DTrace and covered the D language, it’s time to get into what DTrace is really all about—solving problems and understanding workload behavior. Some problems can be quickly correlated to a specific area of hardware or software, but others have a potentially broader source of root causes. These require starting with a systemwide view and drilling down based on what the first-pass analysis reveals. In this chapter, we’ll show how existing non–DTrace-based tools can help make that first pass and how DTrace can then complement them and take analysis further. Specific hardware subsystems, networking, disk I/O, file system, and specific applications are covered in greater detail in later chapters.

So, what do we mean by system and system view? We’re referring to a coarse decomposition of the various components that make up your computer system. Specifically, looking at the major hardware subsystems, we’re talking about the following: