D trace kde4presentation
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This document provides an overview and introduction to dynamic tracing using DTrace. It begins with defining DTrace as a framework for troubleshooting kernels and applications in real time. It then discusses how DTrace works by allowing the dynamic modification of operating systems and processes to record additional data at probes. The document demonstrates some basic DTrace commands like tracing BEGIN and END probes. Finally, it suggests starting to write DTrace probes by finding a place in the Qt source code to instrument.
D trace kde4presentation
- 1. Dynamically Tracing KDE Manish Chakravarty ThoughtWorks Studios 1
- 2. Agenda • Learn about DTrace • Learn what and where to Trace • Trace! 2
- 3. I. What is DTrace? While I go through the slides, please start copying the VM! 3
- 4. DTrace is.. • a comprehensive Dynamic Tracing framework created by Sun Microsystems for troubleshooting kernel and application problems in real time. 4
- 5. Excuse me? 5
- 6. • Dtrace enables us to “look into” the internals of a running production application and allows us to instrument it • It can do very neat stuff in the kernel as well, but that’s not the point of this session 6
- 7. So how does DTrace work? 7
- 8. • Dtrace allows you to dynamically modify the operating system kernel and user processes to record additional data that you specify at locations of interest, called probes 8
- 9. • Dtrace probes come from a set of kernel modules called providers, each of which performs a particular type of instrumentation to create probes 9
- 11. Provider The name of the DTrace provider that is publishing this probe 11
- 12. Module If this probe corresponds to a specific program location, the name of the module which the probe is located The name is either the name of a kernel module or a user library 12
- 13. Function If this probe corresponds to a specific program location, the name of the program function in which the probe is located 13
- 14. Name The final component of the probe name is a name that gives you some idea of the probe’s semantic meaning such as BEGIN or END 14
- 16. DTrace Architecture 16
- 17. Let’s start Tracing! 17
- 18. manish@belenix-KDE4:~/WorkOut/ DTraceTutorial$ pfexec dtrace -n BEGIN dtrace: description 'BEGIN' matched 1 probe CPU ID FUNCTION:NAME 0 1 :BEGIN ^C 18
- 19. manish@belenix-KDE4:~/WorkOut/ DTraceTutorial$ pfexec dtrace -n BEGIN -n END dtrace: description 'BEGIN' matched 1 probe dtrace: description 'END' matched 1 probe CPU ID FUNCTION:NAME 0 1 :BEGIN ^C 0 2 :END 19
- 20. • The probe BEGIN fires every time you start a new tracing request • The probe END fires every time you exit DTrace. In this case hitting Ctrl-C triggered it. 20
- 21. Hello, World! 21
- 22. BEGIN { trace("hello, world"); exit(0); } 22
- 23. Output.. manish@belenix-KDE4:~/WorkOut/DTraceTutorial/1- HelloWorld$ pfexec dtrace -s hello.d dtrace: script 'hello.d' matched 1 probe CPU ID FUNCTION:NAME 0 1 :BEGIN hello, world 23
- 24. 61,809 DTrace probes on the system! pfexec dtrace -l | wc -l 24
- 25. DTrace Architecture Source: http://wikis.sun.com/download/attachments/10390716/architecture.gif 25
- 26. II. What / Where / How 26
- 27. • Navigate to the directory having the Qt source code • Find out a good place in QObject to put one • Start writing probes! 27
- 28. Hack! 28