linux-kernel - Re: [PATCHSET 0/8] perf/core: Prepare sample data for BPF

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Message-ID: <Y8Fb45iZ5yp3TUDD@krava>
Date:   Fri, 13 Jan 2023 14:25:55 +0100
From:   Jiri Olsa <olsajiri@...il.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, Song Liu <song@...nel.org>,
        bpf@...r.kernel.org
Subject: Re: [PATCHSET 0/8] perf/core: Prepare sample data for BPF

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@...nel.org>
> Cc: bpf@...r.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
>