Re: [PATCH V1 10/23] perf auxtrace: Add mmap_needed to auxtrace_mmap_params

[Ian Rogers]

On Thu, May 5, 2022 at 9:57 AM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>
> Add mmap_needed to auxtrace_mmap_params.
>
> Currently an auxtrace mmap is always attempted even if the event is not an
> auxtrace event. That works because, when AUX area tracing, there is always
> an auxtrace event first for every mmap. Prepare for that not being the
> case, which it won't be when sideband tracking events are allowed on
> all CPUs even when auxtrace is limited to selected CPUs.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> ---
>  tools/perf/util/auxtrace.c | 10 ++++++++--
>  tools/perf/util/auxtrace.h |  7 +++++--
>  tools/perf/util/evlist.c   |  5 +++--
>  tools/perf/util/mmap.c     |  1 +
>  4 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
> index b11549ae39df..b446cfa66469 100644
> --- a/tools/perf/util/auxtrace.c
> +++ b/tools/perf/util/auxtrace.c
> @@ -125,7 +125,7 @@ int auxtrace_mmap__mmap(struct auxtrace_mmap *mm,
>         mm->tid = mp->tid;
>         mm->cpu = mp->cpu.cpu;
>
> -       if (!mp->len) {
> +       if (!mp->len || !mp->mmap_needed) {
>                 mm->base = NULL;
>                 return 0;
>         }
> @@ -168,9 +168,15 @@ void auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp,
>  }
>
>  void auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp,
> -                                  struct evlist *evlist, int idx,
> +                                  struct evlist *evlist,
> +                                  struct evsel *evsel, int idx,
>                                    bool per_cpu)
>  {
> +       mp->mmap_needed = evsel->needs_auxtrace_mmap;
> +
> +       if (!mp->mmap_needed)
> +               return;
> +
>         mp->idx = idx;
>
>         if (per_cpu) {
> diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
> index dc38b6f57232..4e715e2d9291 100644
> --- a/tools/perf/util/auxtrace.h
> +++ b/tools/perf/util/auxtrace.h
> @@ -353,6 +353,7 @@ struct auxtrace_mmap_params {
>         int             prot;
>         int             idx;
>         pid_t           tid;
> +       bool            mmap_needed;

It'd be useful to add or fix some context documentation here. Above it says:

* struct auxtrace_mmap_params - parameters to set up struct auxtrace_mmap.

but this flag seems intended for the operation to fail. Clarifying the
intention of the flag would be useful.

Thanks,
Ian

>         struct perf_cpu cpu;
>  };
>
> @@ -490,7 +491,8 @@ void auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp,
>                                 unsigned int auxtrace_pages,
>                                 bool auxtrace_overwrite);
>  void auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp,
> -                                  struct evlist *evlist, int idx,
> +                                  struct evlist *evlist,
> +                                  struct evsel *evsel, int idx,
>                                    bool per_cpu);
>
>  typedef int (*process_auxtrace_t)(struct perf_tool *tool,
> @@ -863,7 +865,8 @@ void auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp,
>                                 unsigned int auxtrace_pages,
>                                 bool auxtrace_overwrite);
>  void auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp,
> -                                  struct evlist *evlist, int idx,
> +                                  struct evlist *evlist,
> +                                  struct evsel *evsel, int idx,
>                                    bool per_cpu);
>
>  #define ITRACE_HELP ""
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 7ae56b062f44..996bdc203616 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -747,15 +747,16 @@ static struct mmap *evlist__alloc_mmap(struct evlist *evlist,
>
>  static void
>  perf_evlist__mmap_cb_idx(struct perf_evlist *_evlist,
> -                        struct perf_evsel *_evsel __maybe_unused,
> +                        struct perf_evsel *_evsel,
>                          struct perf_mmap_param *_mp,
>                          int idx)
>  {
>         struct evlist *evlist = container_of(_evlist, struct evlist, core);
>         struct mmap_params *mp = container_of(_mp, struct mmap_params, core);
>         bool per_cpu = !perf_cpu_map__empty(_evlist->user_requested_cpus);
> +       struct evsel *evsel = container_of(_evsel, struct evsel, core);
>
> -       auxtrace_mmap_params__set_idx(&mp->auxtrace_mp, evlist, idx, per_cpu);
> +       auxtrace_mmap_params__set_idx(&mp->auxtrace_mp, evlist, evsel, idx, per_cpu);
>  }
>
>  static struct perf_mmap*
> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> index 50502b4a7ca4..de59c4da852b 100644
> --- a/tools/perf/util/mmap.c
> +++ b/tools/perf/util/mmap.c
> @@ -62,6 +62,7 @@ void __weak auxtrace_mmap_params__init(struct auxtrace_mmap_params *mp __maybe_u
>
>  void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __maybe_unused,
>                                           struct evlist *evlist __maybe_unused,
> +                                         struct evsel *evsel __maybe_unused,
>                                           int idx __maybe_unused,
>                                           bool per_cpu __maybe_unused)
>  {
> --
> 2.25.1
>