linux-kernel - Re: [PATCH] perf record: Fix perf_can_aux_sample

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Date:   Fri, 22 Nov 2019 10:49:18 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf record: Fix perf_can_aux_sample_size()

Em Fri, Nov 22, 2019 at 10:42:57AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Nov 22, 2019 at 11:48:56AM +0200, Adrian Hunter escreveu:
> > perf_can_aux_sample_size() always returned true because it did not pass
> > the attribute size to sys_perf_event_open, nor correctly check the
> > return value and errno.
> > 
> > Before:
> > 
> >   # perf record --aux-sample -e '{intel_pt//u,branch-misses:u}'
> >   Error:
> >   The sys_perf_event_open() syscall returned with 7 (Argument list too long) for event (branch-misses:u).
> >   /bin/dmesg | grep -i perf may provide additional information.
> > 
> > After:
> > 
> >   # perf record --aux-sample -e '{intel_pt//u,branch-misses:u}'
> >   AUX area sampling is not supported by kernel
> 
> Since this hasn't been sent to Ingo, I combined it with the patch that
> introduced the problem, this one:
> 
> c31d79e7a052 perf record: Add a function to test for kernel support for AUX area sampling
> 
> Thanks for the quick fix,

Wrapping up, at the end of the series I now get:

  [root@...co ~]# perf record --aux-sample -e '{intel_pt//u,branch-misses:u}'
  AUX area sampling is not supported by kernel
  [root@...co ~]#
  [root@...co ~]# uname -a
  Linux quaco 5.4.0-rc8 #1 SMP Mon Nov 18 06:15:31 -03 2019 x86_64 x86_64 x86_64 GNU/Linux
  [root@...co ~]#

Thanks,

- Arnaldo