Re: [Question] How to sample PERF_TYPE_HARDWARE

[Namhyung Kim <namhyung@gmail.com>]

Hello,

On Mon, Feb 8, 2021 at 12:50 PM rainkin <rainkin1993@gmail.com> wrote:
>
> Hello~
>
> My goal is to record the number of occurring PERF_TYPE_HARDWARE events
> (e.g., branches) every N events.
>
> In my understanding, the "perf stat -e branches -I N " command is not
> sampling, it is actually count model which records branches every N
> millisecond. Thus perf stat does not meet my goal.
>
> For the "perf record -e cycles -b" command, it does sampling, which
> records a LBR sample every N cycles events. However, it seems that
> "perf record" does not support sampling PERF_TYPE_HARDWARE.

The 'cycles' is a PERF_TYPE_HARDWARE event.

>
> I also look at the syscall perf_event_open, but still cannot find any
> documentation about how to sample PERF_TYPE_HARDWARE.
>
> Does anyone know how to do that？Any suggestions is helpful for me :)

  perf record -e branches -c N

?

Thanks,
Namhyung