linux-kernel - Re: [PATCH 06/35] perf tools: Add perf_event__synthesize_id

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Date:   Tue, 19 Jul 2022 10:10:51 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 06/35] perf tools: Add perf_event__synthesize_id_sample()

On Mon, Jul 11, 2022 at 2:32 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> Add perf_event__synthesize_id_sample() to enable the synthesis of
> ID samples.
>
> This is needed by perf inject. When injecting events from a guest perf.data
> file, there is a possibility that the sample ID numbers conflict. In that
> case, perf_event__synthesize_id_sample() can be used to re-write the ID
> sample.

This is great documentation, it would be nice to capture it with the
function declaration.

Thanks,
Ian

> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  tools/perf/util/synthetic-events.c | 47 ++++++++++++++++++++++++++++++
>  tools/perf/util/synthetic-events.h |  1 +
>  2 files changed, 48 insertions(+)
>
> diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
> index fe5db4bf0042..ed9623702f34 100644
> --- a/tools/perf/util/synthetic-events.c
> +++ b/tools/perf/util/synthetic-events.c
> @@ -1712,6 +1712,53 @@ int perf_event__synthesize_sample(union perf_event *event, u64 type, u64 read_fo
>         return 0;
>  }
>
> +int perf_event__synthesize_id_sample(__u64 *array, u64 type, const struct perf_sample *sample)
> +{
> +       __u64 *start = array;
> +
> +       /*
> +        * used for cross-endian analysis. See git commit 65014ab3
> +        * for why this goofiness is needed.
> +        */
> +       union u64_swap u;
> +
> +       if (type & PERF_SAMPLE_TID) {
> +               u.val32[0] = sample->pid;
> +               u.val32[1] = sample->tid;
> +               *array = u.val64;
> +               array++;
> +       }
> +
> +       if (type & PERF_SAMPLE_TIME) {
> +               *array = sample->time;
> +               array++;
> +       }
> +
> +       if (type & PERF_SAMPLE_ID) {
> +               *array = sample->id;
> +               array++;
> +       }
> +
> +       if (type & PERF_SAMPLE_STREAM_ID) {
> +               *array = sample->stream_id;
> +               array++;
> +       }
> +
> +       if (type & PERF_SAMPLE_CPU) {
> +               u.val32[0] = sample->cpu;
> +               u.val32[1] = 0;
> +               *array = u.val64;
> +               array++;
> +       }
> +
> +       if (type & PERF_SAMPLE_IDENTIFIER) {
> +               *array = sample->id;
> +               array++;
> +       }
> +
> +       return (void *)array - (void *)start;
> +}
> +
>  int perf_event__synthesize_id_index(struct perf_tool *tool, perf_event__handler_t process,
>                                     struct evlist *evlist, struct machine *machine)
>  {
> diff --git a/tools/perf/util/synthetic-events.h b/tools/perf/util/synthetic-events.h
> index 78a0450db164..b136ec3ec95d 100644
> --- a/tools/perf/util/synthetic-events.h
> +++ b/tools/perf/util/synthetic-events.h
> @@ -55,6 +55,7 @@ int perf_event__synthesize_extra_attr(struct perf_tool *tool, struct evlist *evs
>  int perf_event__synthesize_extra_kmaps(struct perf_tool *tool, perf_event__handler_t process, struct machine *machine);
>  int perf_event__synthesize_features(struct perf_tool *tool, struct perf_session *session, struct evlist *evlist, perf_event__handler_t process);
>  int perf_event__synthesize_id_index(struct perf_tool *tool, perf_event__handler_t process, struct evlist *evlist, struct machine *machine);
> +int perf_event__synthesize_id_sample(__u64 *array, u64 type, const struct perf_sample *sample);
>  int perf_event__synthesize_kernel_mmap(struct perf_tool *tool, perf_event__handler_t process, struct machine *machine);
>  int perf_event__synthesize_mmap_events(struct perf_tool *tool, union perf_event *event, pid_t pid, pid_t tgid, perf_event__handler_t process, struct machine *machine, bool mmap_data);
>  int perf_event__synthesize_modules(struct perf_tool *tool, perf_event__handler_t process, struct machine *machine);
> --
> 2.25.1
>