Re: [PATCH 2/2] perf record: Add --synth option

[Namhyung Kim <namhyung@kernel.org>]

On Fri, Jul 23, 2021 at 9:07 AM Stephane Eranian <eranian@google.com> wrote:
>
> 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.

Ok, will update.

Thanks,
Namhyung

>
>
> >
> >  --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
> >