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Chapter 1. Introduction
SystemTap provides free software (GPL) infrastructure to simplify the gathering of information about the running Linux system. This assists diagnosis of a performance or functional problem. SystemTap eliminates the need for the developer to go through the tedious and disruptive instrument, recompile, install, and reboot sequence that may be otherwise required to collect data.
SystemTap provides a simple command line interface and scripting language for writing instrumentation for a live, running kernel. This instrumentation uses probe points and functions provided in the tapset library.
Simply put, tapsets are scripts that encapsulate knowledge about a kernel subsystem into pre-written probes and functions that can be used by other scripts. Tapsets are analogous to libraries for C programs. They hide the underlying details of a kernel area while exposing the key information needed to manage and monitor that aspect of the kernel. They are typically developed by kernel subject-matter experts.
A tapset exposes the high-level data and state transitions of a subsystem. For the most part, good tapset developers assume that SystemTap users know little to nothing about the kernel subsystem's low-level details. As such, tapset developers write tapsets that help ordinary SystemTap users write meaningful and useful SystemTap scripts.
1.1. Documentation Goals
This guide aims to document SystemTap's most useful and common tapset entries; it also contains guidelines on proper tapset development and documentation. The tapset definitions contained in this guide are extracted automatically from properly-formatted comments in the code of each tapset file. As such, any revisions to the definitions in this guide should be applied directly to their respective tapset file.