2009-03-18 16:36:16

by William Cohen

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Subject: Documenting kernel tracepoints

There are a number of tracepoints in the latest kernels, but not much
documentation on the tracepoints. If a very recent version of
systemtap is available on the system, a list of the probe points can
be obtained with:

stap -p2 -e 'probe kernel.trace("*") {exit()}'|sort

However, this only provides the names. It doesn't provide information
about what information the probe point provides or the arguments
available at the probe point.

Currently, a number of kernel functions and structures are documented
with embedded comments that are extracted with kernel-doc. Seems like
it would be reasonable to extend this to support tracepoints.
Any thoughts or comments about this approach?

-Will


2009-03-18 16:44:51

by Ingo Molnar

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Subject: Re: Documenting kernel tracepoints


* William Cohen <[email protected]> wrote:

> There are a number of tracepoints in the latest kernels, but not
> much documentation on the tracepoints. If a very recent version
> of systemtap is available on the system, a list of the probe
> points can be obtained with:
>
> stap -p2 -e 'probe kernel.trace("*") {exit()}'|sort
>
> However, this only provides the names. It doesn't provide
> information about what information the probe point provides or the
> arguments available at the probe point.
>
> Currently, a number of kernel functions and structures are
> documented with embedded comments that are extracted with
> kernel-doc. Seems like it would be reasonable to extend this to
> support tracepoints. Any thoughts or comments about this approach?

FYI, in the latest tracing tree (targeted for 2.6.30) all
tracepoints show up under /debug/tracing/events/.

Ingo

2009-03-18 19:19:29

by William Cohen

[permalink] [raw]
Subject: Re: Documenting kernel tracepoints

Ingo Molnar wrote:
> * William Cohen <[email protected]> wrote:
>
>> There are a number of tracepoints in the latest kernels, but not
>> much documentation on the tracepoints. If a very recent version
>> of systemtap is available on the system, a list of the probe
>> points can be obtained with:
>>
>> stap -p2 -e 'probe kernel.trace("*") {exit()}'|sort
>>
>> However, this only provides the names. It doesn't provide
>> information about what information the probe point provides or the
>> arguments available at the probe point.
>>
>> Currently, a number of kernel functions and structures are
>> documented with embedded comments that are extracted with
>> kernel-doc. Seems like it would be reasonable to extend this to
>> support tracepoints. Any thoughts or comments about this approach?
>
> FYI, in the latest tracing tree (targeted for 2.6.30) all
> tracepoints show up under /debug/tracing/events/.
>
> Ingo

The /debug/tracing/events provides event names and information about the
available arguments. However, it doesn't provide the detail comparable to
kerneldoc embedded comments summarizing the tracepoint's purpose or what the
arguments are.

-Will