Re: [PATCH V2 10/23] perf auxtrace: Add mmap_needed to auxtrace_mmap_params

Ian Rogers
2022-05-06T20:17:15Z

On Fri, May 6, 2022 at 5:26 AM Adrian Hunter <adrian.hunter@intel.com> 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.

Should there be a later patch to remove this option and just not do
the auxtrace mmap when it's not necessary?

> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
> tools/perf/util/auxtrace.c | 10 ++++++++--
> tools/perf/util/auxtrace.h | 8 ++++++--
> tools/perf/util/evlist.c | 5 +++--
> tools/perf/util/mmap.c | 1 +
> 4 files changed, 18 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..37feae003904 100644
> --- a/tools/perf/util/auxtrace.h
> +++ b/tools/perf/util/auxtrace.h
> @@ -344,6 +344,7 @@ struct auxtrace_mmap {
> * @idx: index of this mmap
> * @tid: tid for a per-thread mmap (also set if there is only 1 tid on a per-cpu
> * mmap) otherwise %0
> + * @mmap_needed: set to %false for non-auxtrace events

Could you add something like:
(ie. we don't want the mmap but we do want the side effects of ...

Thanks,
Ian

> * @cpu: cpu number for a per-cpu mmap otherwise %-1
> */
> struct auxtrace_mmap_params {
> @@ -353,6 +354,7 @@ struct auxtrace_mmap_params {
> int prot;
> int idx;
> pid_t tid;
> + bool mmap_needed;
> struct perf_cpu cpu;
> };
>
> @@ -490,7 +492,8 @@ 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 +866,8 @@ 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
>