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Thanks for the writeup! strace should definitely be in your toolbox. There is also systemtap, which I like a lot as well. It has some problem on Linux though, e

by Argorak 13y ago

Thanks for the writeup! strace should definitely be in your toolbox. There is also systemtap, which I like a lot as well. It has some problem on Linux though, especially only being widely supported of Linux > 3.5 if the distro you are using does not ship with patches. Custom userspace probes are a real strong point. I wrote a short article about stap using Rubys probes as an example: http://www.asquera.de/blog/2014-01-26/stap-and-ruby-2 http://www.asquera.de/blog/2014-01-26/stap-and-ruby-2

donavanm 13y ago
To clarify, systemtap needs UTRACE or UPROBES kernel support to trace user processes. Without those you can still inspect kernel functions. IIRC UTRACE was mainly supported by Redhat, and available intheir kernels for quite a few years. In 3.5 the UPROBES functionality was merged in to mainline. Other tools, like perf, can use UPROBES support as well.
- Argorak 13y ago
  Yep, thats the detailed story. A lot of Linuxes (especially current Ubuntu LTS) ship without those patches, though, which makes the whole exercise of compiling the kernel yourself (and maybe a debug image to go along with it) a tedious one, and probably not fit for a production environment. Thats why I decided to focus on Linux > 3.5, which will be available with Ubuntu 14.04 LTS, where installing gets much easier if you know the right packages. I definitely wanted to make sure that people can start playing around with it in a few minutes. Also, UPROBES are in my opinion one of the most interesting features to grab with strace. It allows you to easily combine detailed kernel-level tracing with tracing of your application. (Not that I want to suggest that compiling your own kernel is hard to do, it just takes the fun out of "let's trace!")