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From:   Stephane Eranian <eranian@google.com>
Date:   Fri, 23 Jul 2021 09:07:35 -0700
Message-ID: <CABPqkBSTK+Z2TAxjYb3ysyq0iz+sA+O-M2-TQz9QBvwK6g8SOA@mail.gmail.com>
Subject: Re: [PATCH 2/2] perf record: Add --synth option
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>, Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andi Kleen <ak@linux.intel.com>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Jin Yao <yao.jin@linux.intel.com>
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On Thu, Jul 22, 2021 at 7:40 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Add an option to control synthesize behavior.
>
>     --synth <no|all|task|mmap|cgroup>
>                       Fine-tune event synthesis: default=all
>
> This can be useful when we know it doesn't need some synthesis like
> in a specific usecase and/or when using pipe:
>
>   $ perf record -a --all-cgroups --synth cgroup -o- sleep 1 | \
>   > perf report -i- -s cgroup
>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/perf/Documentation/perf-record.txt |  4 ++
>  tools/perf/builtin-record.c              | 48 +++++++++++++++++++-----
>  tools/perf/util/record.h                 |  1 +
>  tools/perf/util/synthetic-events.c       | 28 ++++++++++++++
>  tools/perf/util/synthetic-events.h       | 12 ++++++
>  5 files changed, 84 insertions(+), 9 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index d71bac847936..421a7b93c4b5 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -596,6 +596,10 @@ options.
>  'perf record --dry-run -e' can act as a BPF script compiler if llvm.dump-obj
>  in config file is set to true.
>
> +--synth=TYPE::
> +Collect and synthesize given type of events.  Available types are:
> +task, mmap, cgroup, all, no
> +

I would explain what each option disables in the synthesis. It is not
clear in your description
or your explain in the commit msg.


>
>  --tail-synthesize::
>  Instead of collecting non-sample events (for example, fork, comm, mmap) at
>  the beginning of record, collect them during finalizing an output file.
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 535da4dfd8d3..caaada3594ce 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1254,6 +1254,7 @@ static int record__synthesize_workload(struct record *rec, bool tail)
>  {
>         int err;
>         struct perf_thread_map *thread_map;
> +       bool needs_mmap = rec->opts.synth & PERF_SYNTH_MMAP;
>
>         if (rec->opts.tail_synthesize != tail)
>                 return 0;
> @@ -1265,7 +1266,7 @@ static int record__synthesize_workload(struct record *rec, bool tail)
>         err = perf_event__synthesize_thread_map(&rec->tool, thread_map,
>                                                  process_synthesized_event,
>                                                  &rec->session->machines.host,
> -                                                true,
> +                                                needs_mmap,
>                                                  rec->opts.sample_address);
>         perf_thread_map__put(thread_map);
>         return err;
> @@ -1500,20 +1501,26 @@ static int record__synthesize(struct record *rec, bool tail)
>         if (err < 0)
>                 pr_warning("Couldn't synthesize bpf events.\n");
>
> -       err = perf_event__synthesize_cgroups(tool, process_synthesized_event,
> -                                            machine);
> -       if (err < 0)
> -               pr_warning("Couldn't synthesize cgroup events.\n");
> +       if (rec->opts.synth & PERF_SYNTH_CGROUP) {
> +               err = perf_event__synthesize_cgroups(tool, process_synthesized_event,
> +                                                    machine);
> +               if (err < 0)
> +                       pr_warning("Couldn't synthesize cgroup events.\n");
> +       }
>
>         if (rec->opts.nr_threads_synthesize > 1) {
>                 perf_set_multithreaded();
>                 f = process_locked_synthesized_event;
>         }
>
> -       err = __machine__synthesize_threads(machine, tool, &opts->target,
> -                                           rec->evlist->core.threads,
> -                                           f, true, opts->sample_address,
> -                                           rec->opts.nr_threads_synthesize);
> +       if (rec->opts.synth & PERF_SYNTH_TASK) {
> +               bool needs_mmap = rec->opts.synth & PERF_SYNTH_MMAP;
> +
> +               err = __machine__synthesize_threads(machine, tool, &opts->target,
> +                                                   rec->evlist->core.threads,
> +                                                   f, needs_mmap, opts->sample_address,
> +                                                   rec->opts.nr_threads_synthesize);
> +       }
>
>         if (rec->opts.nr_threads_synthesize > 1)
>                 perf_set_singlethreaded();
> @@ -2422,6 +2429,26 @@ static int process_timestamp_boundary(struct perf_tool *tool,
>         return 0;
>  }
>
> +static int parse_record_synth_option(const struct option *opt,
> +                                    const char *str,
> +                                    int unset __maybe_unused)
> +{
> +       struct record_opts *opts = opt->value;
> +       char *p = strdup(str);
> +
> +       if (p == NULL)
> +               return -1;
> +
> +       opts->synth = parse_synth_opt(p);
> +       free(p);
> +
> +       if (opts->synth < 0) {
> +               pr_err("Invalid synth option: %s\n", str);
> +               return -1;
> +       }
> +       return 0;
> +}
> +
>  /*
>   * XXX Ideally would be local to cmd_record() and passed to a record__new
>   * because we need to have access to it in record__exit, that is called
> @@ -2447,6 +2474,7 @@ static struct record record = {
>                 .nr_threads_synthesize = 1,
>                 .ctl_fd              = -1,
>                 .ctl_fd_ack          = -1,
> +               .synth               = PERF_SYNTH_ALL,
>         },
>         .tool = {
>                 .sample         = process_sample_event,
> @@ -2662,6 +2690,8 @@ static struct option __record_options[] = {
>                      "\t\t\t  Optionally send control command completion ('ack\\n') to ack-fd descriptor.\n"
>                      "\t\t\t  Alternatively, ctl-fifo / ack-fifo will be opened and used as ctl-fd / ack-fd.",
>                       parse_control_option),
> +       OPT_CALLBACK(0, "synth", &record.opts, "no|all|task|mmap|cgroup",
> +                    "Fine-tune event synthesis: default=all", parse_record_synth_option),
>         OPT_END()
>  };
>
> diff --git a/tools/perf/util/record.h b/tools/perf/util/record.h
> index 68f471d9a88b..ef6c2715fdd9 100644
> --- a/tools/perf/util/record.h
> +++ b/tools/perf/util/record.h
> @@ -77,6 +77,7 @@ struct record_opts {
>         int           ctl_fd;
>         int           ctl_fd_ack;
>         bool          ctl_fd_close;
> +       int           synth;
>  };
>
>  extern const char * const *record_usage;
> diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
> index 566e0859fcfb..9485d0532b9c 100644
> --- a/tools/perf/util/synthetic-events.c
> +++ b/tools/perf/util/synthetic-events.c
> @@ -2186,3 +2186,31 @@ int perf_event__synthesize_features(struct perf_tool *tool, struct perf_session
>         free(ff.buf);
>         return ret;
>  }
> +
> +int parse_synth_opt(char *synth)
> +{
> +       char *p, *q;
> +       int ret = 0;
> +
> +       if (synth == NULL)
> +               return -1;
> +
> +       for (q = synth; (p = strsep(&q, ",")); p = q) {
> +               if (!strcasecmp(p, "no") || !strcasecmp(p, "none"))
> +                       return 0;
> +
> +               if (!strcasecmp(p, "all"))
> +                       return PERF_SYNTH_ALL;
> +
> +               if (!strcasecmp(p, "task"))
> +                       ret |= PERF_SYNTH_TASK;
> +               else if (!strcasecmp(p, "mmap"))
> +                       ret |= PERF_SYNTH_TASK | PERF_SYNTH_MMAP;
> +               else if (!strcasecmp(p, "cgroup"))
> +                       ret |= PERF_SYNTH_CGROUP;
> +               else
> +                       return -1;
> +       }
> +
> +       return ret;
> +}
> diff --git a/tools/perf/util/synthetic-events.h b/tools/perf/util/synthetic-events.h
> index 61bbdb3b64df..913803506345 100644
> --- a/tools/perf/util/synthetic-events.h
> +++ b/tools/perf/util/synthetic-events.h
> @@ -26,6 +26,18 @@ struct target;
>
>  union perf_event;
>
> +enum perf_record_synth {
> +       PERF_SYNTH_TASK         = 1 << 0,
> +       PERF_SYNTH_MMAP         = 1 << 1,
> +       PERF_SYNTH_CGROUP       = 1 << 2,
> +
> +       /* last element */
> +       PERF_SYNTH_MAX          = 1 << 3,
> +};
> +#define PERF_SYNTH_ALL  (PERF_SYNTH_MAX - 1)
> +
> +int parse_synth_opt(char *str);
> +
>  typedef int (*perf_event__handler_t)(struct perf_tool *tool, union perf_event *event,
>                                      struct perf_sample *sample, struct machine *machine);
>
> --
> 2.32.0.432.gabb21c7263-goog
>