[PATCHSET,0/8] perf/core: Prepare sample data for BPF

  Hello,

The perf_prepare_sample() is to fill the perf sample data and update the
header info before sending it to the ring buffer.  But we want to use it
for BPF overflow handler so that it can access the sample data to filter
relevant ones.

Changes in v2)
 * the layout change is merged
 * reduce branches using __cond_set  (PeterZ)
 * add helpers to set dynamic sample data  (PeterZ)
 * introduce perf_prepare_header()  (PeterZ)
 * call perf_prepare_sample() before bpf_overflow_handler unconditionally

This means the perf_prepare_handler() can be called more than once.  To
avoid duplicate work, use the data->sample_flags and save the data size.

I also added a few of helpers to set those information accordingly.
But it looks some fields like REGS_USER, STACK_USER and AUX are saved in
the perf_prepare_sample() so I didn't add the helpers for them.

After than we can just check the filtered_sample_type flags begin zero
to determine if it has more work.  In that case, it needs to update the
data->type since it's possible to miss when PMU driver sets all required
sample flags before calling perf_prepare_sample().

The code is also available at 'perf/prepare-sample-v2' branch in

  git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git

Thanks,
Namhyung


Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org


Namhyung Kim (8):
  perf/core: Save the dynamic parts of sample data size
  perf/core: Add perf_sample_save_callchain() helper
  perf/core: Add perf_sample_save_raw_data() helper
  perf/core: Add perf_sample_save_brstack() helper
  perf/core: Set data->sample_flags in perf_prepare_sample()
  perf/core: Do not pass header for sample id init
  perf/core: Introduce perf_prepare_header()
  perf/core: Call perf_prepare_sample() before running BPF

 arch/powerpc/perf/core-book3s.c    |   3 +-
 arch/s390/kernel/perf_cpum_cf.c    |   4 +-
 arch/s390/kernel/perf_cpum_sf.c    |   3 +-
 arch/s390/kernel/perf_pai_crypto.c |   4 +-
 arch/s390/kernel/perf_pai_ext.c    |   4 +-
 arch/x86/events/amd/core.c         |   6 +-
 arch/x86/events/amd/ibs.c          |   9 +-
 arch/x86/events/intel/core.c       |   6 +-
 arch/x86/events/intel/ds.c         |  24 ++--
 include/linux/perf_event.h         | 133 +++++++++++++-----
 kernel/events/core.c               | 207 ++++++++++++++++-------------
 kernel/trace/bpf_trace.c           |   6 +-
 12 files changed, 236 insertions(+), 173 deletions(-)


base-commit: 9fcad995c6c52cc9791f7ee9f1386a5684055f9c
  

On Thu, Jan 12, 2023 at 01:40:07PM -0800, Namhyung Kim wrote:

> Namhyung Kim (8):
>   perf/core: Save the dynamic parts of sample data size
>   perf/core: Add perf_sample_save_callchain() helper
>   perf/core: Add perf_sample_save_raw_data() helper
>   perf/core: Add perf_sample_save_brstack() helper
>   perf/core: Set data->sample_flags in perf_prepare_sample()
>   perf/core: Do not pass header for sample id init
>   perf/core: Introduce perf_prepare_header()
>   perf/core: Call perf_prepare_sample() before running BPF

Aside from a few small niggles, this looks really good, Thanks!
  

On Thu, Jan 12, 2023 at 01:40:07PM -0800, Namhyung Kim wrote:
> Hello,
> 
> The perf_prepare_sample() is to fill the perf sample data and update the
> header info before sending it to the ring buffer.  But we want to use it
> for BPF overflow handler so that it can access the sample data to filter
> relevant ones.
> 
> Changes in v2)
>  * the layout change is merged
>  * reduce branches using __cond_set  (PeterZ)
>  * add helpers to set dynamic sample data  (PeterZ)
>  * introduce perf_prepare_header()  (PeterZ)
>  * call perf_prepare_sample() before bpf_overflow_handler unconditionally
> 
> This means the perf_prepare_handler() can be called more than once.  To
> avoid duplicate work, use the data->sample_flags and save the data size.
> 
> I also added a few of helpers to set those information accordingly.
> But it looks some fields like REGS_USER, STACK_USER and AUX are saved in
> the perf_prepare_sample() so I didn't add the helpers for them.
> 
> After than we can just check the filtered_sample_type flags begin zero
> to determine if it has more work.  In that case, it needs to update the
> data->type since it's possible to miss when PMU driver sets all required
> sample flags before calling perf_prepare_sample().
> 
> The code is also available at 'perf/prepare-sample-v2' branch in
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
> 
> Thanks,
> Namhyung
> 
> 
> Cc: Song Liu <song@kernel.org>
> Cc: bpf@vger.kernel.org
> 
> 
> Namhyung Kim (8):
>   perf/core: Save the dynamic parts of sample data size
>   perf/core: Add perf_sample_save_callchain() helper
>   perf/core: Add perf_sample_save_raw_data() helper
>   perf/core: Add perf_sample_save_brstack() helper
>   perf/core: Set data->sample_flags in perf_prepare_sample()
>   perf/core: Do not pass header for sample id init
>   perf/core: Introduce perf_prepare_header()
>   perf/core: Call perf_prepare_sample() before running BPF

lgtm, I ran the bpf selftests on top of that and it's ok

jirka

> 
>  arch/powerpc/perf/core-book3s.c    |   3 +-
>  arch/s390/kernel/perf_cpum_cf.c    |   4 +-
>  arch/s390/kernel/perf_cpum_sf.c    |   3 +-
>  arch/s390/kernel/perf_pai_crypto.c |   4 +-
>  arch/s390/kernel/perf_pai_ext.c    |   4 +-
>  arch/x86/events/amd/core.c         |   6 +-
>  arch/x86/events/amd/ibs.c          |   9 +-
>  arch/x86/events/intel/core.c       |   6 +-
>  arch/x86/events/intel/ds.c         |  24 ++--
>  include/linux/perf_event.h         | 133 +++++++++++++-----
>  kernel/events/core.c               | 207 ++++++++++++++++-------------
>  kernel/trace/bpf_trace.c           |   6 +-
>  12 files changed, 236 insertions(+), 173 deletions(-)
> 
> 
> base-commit: 9fcad995c6c52cc9791f7ee9f1386a5684055f9c
> -- 
> 2.39.0.314.g84b9a713c41-goog
>
  

Hi Jiri,

On Fri, Jan 13, 2023 at 5:26 AM Jiri Olsa <olsajiri@gmail.com> wrote:
>
> On Thu, Jan 12, 2023 at 01:40:07PM -0800, Namhyung Kim wrote:
> > Hello,
> >
> > The perf_prepare_sample() is to fill the perf sample data and update the
> > header info before sending it to the ring buffer.  But we want to use it
> > for BPF overflow handler so that it can access the sample data to filter
> > relevant ones.
> >
> > Changes in v2)
> >  * the layout change is merged
> >  * reduce branches using __cond_set  (PeterZ)
> >  * add helpers to set dynamic sample data  (PeterZ)
> >  * introduce perf_prepare_header()  (PeterZ)
> >  * call perf_prepare_sample() before bpf_overflow_handler unconditionally
> >
> > This means the perf_prepare_handler() can be called more than once.  To
> > avoid duplicate work, use the data->sample_flags and save the data size.
> >
> > I also added a few of helpers to set those information accordingly.
> > But it looks some fields like REGS_USER, STACK_USER and AUX are saved in
> > the perf_prepare_sample() so I didn't add the helpers for them.
> >
> > After than we can just check the filtered_sample_type flags begin zero
> > to determine if it has more work.  In that case, it needs to update the
> > data->type since it's possible to miss when PMU driver sets all required
> > sample flags before calling perf_prepare_sample().
> >
> > The code is also available at 'perf/prepare-sample-v2' branch in
> >
> >   git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
> >
> > Thanks,
> > Namhyung
> >
> >
> > Cc: Song Liu <song@kernel.org>
> > Cc: bpf@vger.kernel.org
> >
> >
> > Namhyung Kim (8):
> >   perf/core: Save the dynamic parts of sample data size
> >   perf/core: Add perf_sample_save_callchain() helper
> >   perf/core: Add perf_sample_save_raw_data() helper
> >   perf/core: Add perf_sample_save_brstack() helper
> >   perf/core: Set data->sample_flags in perf_prepare_sample()
> >   perf/core: Do not pass header for sample id init
> >   perf/core: Introduce perf_prepare_header()
> >   perf/core: Call perf_prepare_sample() before running BPF
>
> lgtm, I ran the bpf selftests on top of that and it's ok

Thanks for your review.  I'll add your Acked-by and Tested-by
in the v3. :)

Thanks,
Namhyung