Messages in this thread | | | Date | Mon, 18 May 2015 13:00:38 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: perf.data file format specification draft |
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Em Mon, May 18, 2015 at 01:21:33PM +0900, Namhyung Kim escreveu: > 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:
Thanks for this! I'll try to write patches for the low hanging fruits, and try to work a bit on other issues, like only collecting the format files for events that the user asked for, perhaps even just for those that had samples :-)
- Arnaldo
> * 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 majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/
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