Re: When and how to use ftrace?

[wu zhangjin]

Hi,

On Wed, Jun 9, 2010 at 4:14 PM, Ryan Wang <openspace.wang@xxxxxxxxx> wrote:
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> Seems ftrace is helpful to study the activities inside the kernel to me.
> I wonder whether it can be useful to debug kernel bugs. And if so, will
> you please give me some examples?

Yeah, did you read this paper written by Steven: "Finding Origins of
Latencies Using Ftrace" (please google to download it).
If not, please read it. that paper will tell you what Ftrace really is
and will show the demos how to play with it.

> Or so far it's mainly used for
> observing the running status of kernel?

Ftrace is originally created for debugging and optimizing the
preempt-rt, but of course, it becomes a tracing framework currently.

It not only show you what the kernel space does when you do something
in user space,
but will show you the calling tree of kernel functions, time consuming
of  every function and
even allow you to filter the parts you care about.

If you need more info about it, please refer to:

[1] Debugging the kernel using Ftrace
http://lwn.net/Articles/365835/
http://lwn.net/Articles/366796/
[2] Ftrace usage ....
Documentation/trace/ftrace.txt
Documentation/trace/ftrace-desgin.txt
[3] Tools for Ftrace
trace-cmd from readhat...

Regards,

-- 
Studying engineer. Wu Zhangjin
Lanzhou University      http://www.lzu.edu.cn
Distributed & Embedded System Lab      http://dslab.lzu.edu.cn
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