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Chapter 41. SystemTap

41.1. Introduction

SystemTap provides a simple command line interface and scripting language to simplify the gathering of information about the running Linux kernel so that it can be further analyzed. Data may be extracted, filtered, and summarized quickly and safely, to enable diagnoses of complex performance or functional problems.
SystemTap allows scripts to be written in the SystemTap scripting language, which are then compiled to C-code kernel modules and inserted into the kernel.
The essential idea behind a systemtap script is to name events, and to give them handlers. Whenever a specified event occurs, the Linux kernel runs the handler as if it were a quick subroutine, then resumes. There are several kind of events, such as entering or exiting a function, a timer expiring, or the entire systemtap session starting or stopping. A handler is a series of script language statements that specify the work to be done whenever the event occurs. This work normally includes extracting data from the event context, storing them into internal variables, or printing results.