Re: [ftrace] possible to implement user-space tracers?

[Scotty Bauer]

It is possible to trace from userland, Android does it.

Essentially you need to write your data into 
/sys/kernel/debug/tracing/trace_marker

then read it out of /sys/kernel/debug/tracing/trace


If you care how the implementation works you can read it in 
/kernel/tracing/trace.c 
(http://lxr.free-electrons.com/source/kernel/trace/trace.c) search for 
tracing_mark_fops and tracing_fops.


In Android here are the relevant files you will need to see how it's 
used in userland:
Atrace (for reading data out + setting things up):
https://android.googlesource.com/platform/frameworks/native/+/master/cmds/atrace/atrace.cpp
https://android.googlesource.com/platform/external/chromium-trace/+/master 
(host side setup of the device)

trace-dev (for writing data in):
https://android.googlesource.com/platform/system/core/+/master/libcutils/trace-dev.c

Once we have all the data we usually run it through trace-viewer, 
(https://github.com/catapult-project/catapult)

Cheers.


> On 2015-08-11 06:53, Kun Huang wrote:
> > Hi ftrace developers
> >
> > I'm developing a huge python based programs and facing performance
> > issue everyday. I like the ftrace system and hope there could be a
> > tracer to trace&report my python codes. Is it possible or is it
> worthy
> > to do this?
> >
> > ---
> >
> > Kun
> > --
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> [6]
> > Please read the FAQ at  http://www.tux.org/lkml/ [7]
>
> Links:
> ------
> [1] http://lxr.free-electrons.com/source/kernel/trace/trace.c
> [2]
> https://android.googlesource.com/platform/frameworks/native/+/master/cmds/atrace/atrace.cpp
> [3] 
> https://android.googlesource.com/platform/external/chromium-trace/+/master
> [4]
> https://android.googlesource.com/platform/system/core/+/master/libcutils/trace-dev.c
> [5] https://github.com/catapult-project/catapult
> [6] http://vger.kernel.org/majordomo-info.html
> [7] http://www.tux.org/lkml/
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