Re: brstack information with perf-intel-pt?

[Adrian Hunter <adrian.hunter@intel.com>]

On 13/02/23 20:33, Iti Shree wrote:
> Hello,
> I am trying to get brstack information in perf.data with intel-pt
> flag. I am passing following command for the following: perf record -e
> intel-pt// -m, 32768
> 
> When I try to check if brstack is present in the gathered data with :
> perf script -F pid, ip, brstack -i pt-perf.data I can only see pid and
> ip information.
> 
> I can seem to find branching information with --itrace=b however I was
> wondering if there is any way I can get brstack information decoded
> into perf.data when I use intel-pt flag similar to what I get with
> default perf record?

You need to use --itrace=li which will synthesize "instructions" events
and add a branch stack.  Note that the period of the instructions events
can be defined e.g. --itrace=li10us for 10 microseconds.  And also the
max size of the branch stack e.g. --itrace=l10i for 10 branches.

Typically you need to be aware of decoding errors also, so also add
the 'e' option i.e. --itrace=el10i10us.  There is also 'L' which adds
the branch stack to non-synthesized events (that you may have added
with the -e option).

Some more information about --itrace for Intel PT is here:

https://perf.wiki.kernel.org/index.php/Latest_Manual_Page_of_perf-intel-pt.1#New_--itrace_option

General information and examples for about Intel PT can be found here:

https://perf.wiki.kernel.org/index.php/Perf_tools_support_for_Intel%C2%AE_Processor_Trace