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

Adrian Hunter
2022-05-11T07:04:15Z

On 6/05/22 23:16, Ian Rogers wrote:
> 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?

The same code path is used for non-auxtrace mmap as auxtrace mmap.
I have amended the comment to explain.

>
>> 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
>>