[PATCH 41/60] perf tools: Add support for leader-sampling with AUX area events
From: Arnaldo Carvalho de Melo
Date: Mon Apr 20 2020 - 07:56:29 EST
From: Adrian Hunter <adrian.hunter@xxxxxxxxx>
When AUX area events are used in sampling mode, they must be the group
leader, but the group leader is also used for leader-sampling. However,
it is not desirable to use an AUX area event as the leader for
leader-sampling, because it doesn't have any samples of its own. To support
leader-sampling with AUX area events, use the 2nd event of the group as the
"leader" for the purposes of leader-sampling.
Example:
# perf record --kcore --aux-sample -e '{intel_pt//,cycles,instructions}:S' -c 10000 uname
[ perf record: Woken up 3 times to write data ]
[ perf record: Captured and wrote 0.786 MB perf.data ]
# perf report
Samples: 380 of events 'anon group { cycles, instructions }', Event count (approx.): 3026164
Children Self Command Shared Object Symbol
+ 38.76% 42.65% 0.00% 0.00% uname [kernel.kallsyms] [k] __x86_indirect_thunk_rax
+ 35.82% 31.33% 0.00% 0.00% uname ld-2.28.so [.] _dl_start_user
+ 34.29% 29.74% 0.55% 0.47% uname ld-2.28.so [.] _dl_start
+ 33.73% 28.62% 1.60% 0.97% uname ld-2.28.so [.] dl_main
+ 33.19% 29.04% 0.52% 0.32% uname ld-2.28.so [.] _dl_sysdep_start
+ 27.83% 33.74% 0.00% 0.00% uname [kernel.kallsyms] [k] do_syscall_64
+ 26.76% 33.29% 0.00% 0.00% uname [kernel.kallsyms] [k] entry_SYSCALL_64_after_hwframe
+ 23.78% 20.33% 5.97% 5.25% uname [kernel.kallsyms] [k] page_fault
+ 23.18% 24.60% 0.00% 0.00% uname libc-2.28.so [.] __libc_start_main
+ 22.64% 24.37% 0.00% 0.00% uname uname [.] _start
+ 21.04% 23.27% 0.00% 0.00% uname uname [.] main
+ 19.48% 18.08% 3.72% 3.64% uname ld-2.28.so [.] _dl_relocate_object
+ 19.47% 21.81% 0.00% 0.00% uname libc-2.28.so [.] setlocale
+ 19.44% 21.56% 0.52% 0.61% uname libc-2.28.so [.] _nl_find_locale
+ 17.87% 19.66% 0.00% 0.00% uname libc-2.28.so [.] _nl_load_locale_from_archive
+ 15.71% 13.73% 0.53% 0.52% uname [kernel.kallsyms] [k] do_page_fault
+ 15.18% 13.21% 1.03% 0.68% uname [kernel.kallsyms] [k] handle_mm_fault
+ 14.15% 12.53% 1.01% 1.12% uname [kernel.kallsyms] [k] __handle_mm_fault
+ 12.03% 9.67% 0.54% 0.32% uname ld-2.28.so [.] _dl_map_object
+ 10.55% 8.48% 0.00% 0.00% uname ld-2.28.so [.] openaux
+ 10.55% 20.20% 0.52% 0.61% uname libc-2.28.so [.] __run_exit_handlers
Comnmitter notes:
Fixed up this problem:
util/record.c: In function âperf_evlist__configâ:
util/record.c:256:3: error: too few arguments to function âperf_evsel__config_leader_samplingâ
256 | perf_evsel__config_leader_sampling(evsel);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
util/record.c:190:13: note: declared here
190 | static void perf_evsel__config_leader_sampling(struct evsel *evsel,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Link: http://lore.kernel.org/lkml/20200401101613.6201-17-adrian.hunter@xxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/Documentation/perf-list.txt | 3 ++
tools/perf/util/record.c | 45 ++++++++++++++++++++++----
2 files changed, 42 insertions(+), 6 deletions(-)
diff --git a/tools/perf/Documentation/perf-list.txt b/tools/perf/Documentation/perf-list.txt
index 6345db33c533..cb23667531ab 100644
--- a/tools/perf/Documentation/perf-list.txt
+++ b/tools/perf/Documentation/perf-list.txt
@@ -258,6 +258,9 @@ Normally all events in an event group sample, but with :S only
the first event (the leader) samples, and it only reads the values of the
other events in the group.
+However, in the case AUX area events (e.g. Intel PT or CoreSight), the AUX
+area event must be the leader, so then the second event samples, not the first.
+
OPTIONS
-------
diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
index 32aeeb8a8d00..6d3e3df6e2a1 100644
--- a/tools/perf/util/record.c
+++ b/tools/perf/util/record.c
@@ -167,17 +167,46 @@ bool perf_can_aux_sample(void)
return true;
}
-static void perf_evsel__config_leader_sampling(struct evsel *evsel)
+/*
+ * perf_evsel__config_leader_sampling() uses special rules for leader sampling.
+ * However, if the leader is an AUX area event, then assume the event to sample
+ * is the next event.
+ */
+static struct evsel *perf_evsel__read_sampler(struct evsel *evsel,
+ struct evlist *evlist)
+{
+ struct evsel *leader = evsel->leader;
+
+ if (perf_evsel__is_aux_event(leader)) {
+ evlist__for_each_entry(evlist, evsel) {
+ if (evsel->leader == leader && evsel != evsel->leader)
+ return evsel;
+ }
+ }
+
+ return leader;
+}
+
+static void perf_evsel__config_leader_sampling(struct evsel *evsel,
+ struct evlist *evlist)
{
struct perf_event_attr *attr = &evsel->core.attr;
struct evsel *leader = evsel->leader;
+ struct evsel *read_sampler;
+
+ if (!leader->sample_read)
+ return;
+
+ read_sampler = perf_evsel__read_sampler(evsel, evlist);
- if (leader == evsel || !leader->sample_read)
+ if (evsel == read_sampler)
return;
/*
- * Disable sampling for all group members other
- * than leader in case leader 'leads' the sampling.
+ * Disable sampling for all group members other than the leader in
+ * case the leader 'leads' the sampling, except when the leader is an
+ * AUX area event, in which case the 2nd event in the group is the one
+ * that 'leads' the sampling.
*/
attr->freq = 0;
attr->sample_freq = 0;
@@ -188,8 +217,12 @@ static void perf_evsel__config_leader_sampling(struct evsel *evsel)
* We don't get a sample for slave events, we make them when delivering
* the group leader sample. Set the slave event to follow the master
* sample_type to ease up reporting.
+ * An AUX area event also has sample_type requirements, so also include
+ * the sample type bits from the leader's sample_type to cover that
+ * case.
*/
- attr->sample_type = leader->core.attr.sample_type;
+ attr->sample_type = read_sampler->core.attr.sample_type |
+ leader->core.attr.sample_type;
}
void perf_evlist__config(struct evlist *evlist, struct record_opts *opts,
@@ -220,7 +253,7 @@ void perf_evlist__config(struct evlist *evlist, struct record_opts *opts,
/* Configure leader sampling here now that the sample type is known */
evlist__for_each_entry(evlist, evsel)
- perf_evsel__config_leader_sampling(evsel);
+ perf_evsel__config_leader_sampling(evsel, evlist);
if (opts->full_auxtrace) {
/*
--
2.21.1