Hi Arnaldo and Andi,
On Thu, May 14, 2015 at 10:11:29AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, May 14, 2015 at 02:25:17PM +0200, Andi Kleen escreveu:
> > Hi,
> >
> > Since there are more and more consumers I started a description of the
> > on-disk perf.data format. This does not replace the kernel perf event
> > description or the manpage, but describes the parts that perf record
> > adds.
> >
> > So far it is still has some gaps and needs review. Eventually this should
> > become part of the perf documentation.
> >
> > Steven, would be good if you could fill in some details on how trace
> > data works.
>
> I guess that would be Frédéric, and also I think this is a good
> opportunity to remove some stuff that seem to be collected but unused,
> namely a kallsyms copy and maybe something else.
Let me try to describe. The tracing_data_get() does the work and it
records the following for HEADER_TRACING_DATA in order:
* tracing header data
- file magic bytes (including someone's birthday :) )
- file version (it's 0.5 - the only thing I can see in diff with trace-cmd
(version 6) is "saved-cmdline" file data which is unnecessary for perf
- byte order, size of long and page size of the system
* tracing header files
- $tracefs/events/header_page and $tracefs/events/header_event
- describe ftrace raw buffer format which is unnecessary for perf unless
it reads the raw buffer directly (like my ftrace integration work?)
* ftrace event files
- format file for each event in $tracefs/events/ftrace directory
- this is same as below but precedes other events, not sure why it's needed
* (normal) event files
- format file for each tracepoint event
* /proc/kallsyms
- for kernel symbol resolution, unnecessary for perf
* tracing printk formats
- for trace_printk? unnecessary for perf
The last two can go away at least.
Thanks,
Namhyung
>
> > Adrian, would be good if you could fill in the missing bits for
> > auxtrace/itrace.
> > Everyone else, please review and add missing information.
>
> Thanks for doing this work!
>
> IIRC there is a presentation written by Jiri where parts of this is
> documented, lemme try to find it...
>
> - Arnaldo
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
