Documenting kernel tracepoints

Documenting kernel tracepoints

[William Cohen]

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

Re: Documenting kernel tracepoints

[Ingo Molnar]

* William Cohen <wcohen@redhat.com> 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

Re: Documenting kernel tracepoints

[William Cohen]

Ingo Molnar wrote:
> * William Cohen <wcohen@redhat.com> 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