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Subject[PATCH 5/7] perf lock: Handle lock contention tracepoints
Date
When the lock contention events are used, there's no tracking of
acquire and release. So the state machine is simplified to use
UNINITIALIZED -> CONTENDED -> ACQUIRED only.

Note that CONTENDED state is re-entrant since mutex locks can hit two
or more consecutive contention_begin events for optimistic spinning
and sleep.

Acked-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/builtin-lock.c | 125 ++++++++++++++++++++++++++++++++++++++
1 file changed, 125 insertions(+)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 7df182a8443b..a677ad9507c3 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -825,6 +825,124 @@ static int report_lock_release_event(struct evsel *evsel,
return 0;
}

+static int report_lock_contention_begin_event(struct evsel *evsel,
+ struct perf_sample *sample)
+{
+ struct lock_stat *ls;
+ struct thread_stat *ts;
+ struct lock_seq_stat *seq;
+ u64 addr = evsel__intval(evsel, sample, "lock_addr");
+
+ if (show_thread_stats)
+ addr = sample->tid;
+
+ ls = lock_stat_findnew(addr, "No name");
+ if (!ls)
+ return -ENOMEM;
+
+ ts = thread_stat_findnew(sample->tid);
+ if (!ts)
+ return -ENOMEM;
+
+ seq = get_seq(ts, addr);
+ if (!seq)
+ return -ENOMEM;
+
+ switch (seq->state) {
+ case SEQ_STATE_UNINITIALIZED:
+ case SEQ_STATE_ACQUIRED:
+ break;
+ case SEQ_STATE_CONTENDED:
+ /*
+ * It can have nested contention begin with mutex spinning,
+ * then we would use the original contention begin event and
+ * ignore the second one.
+ */
+ goto end;
+ case SEQ_STATE_ACQUIRING:
+ case SEQ_STATE_READ_ACQUIRED:
+ case SEQ_STATE_RELEASED:
+ /* broken lock sequence */
+ if (!ls->broken) {
+ ls->broken = 1;
+ bad_hist[BROKEN_CONTENDED]++;
+ }
+ list_del_init(&seq->list);
+ free(seq);
+ goto end;
+ default:
+ BUG_ON("Unknown state of lock sequence found!\n");
+ break;
+ }
+
+ if (seq->state != SEQ_STATE_CONTENDED) {
+ seq->state = SEQ_STATE_CONTENDED;
+ seq->prev_event_time = sample->time;
+ ls->nr_contended++;
+ }
+end:
+ return 0;
+}
+
+static int report_lock_contention_end_event(struct evsel *evsel,
+ struct perf_sample *sample)
+{
+ struct lock_stat *ls;
+ struct thread_stat *ts;
+ struct lock_seq_stat *seq;
+ u64 contended_term;
+ u64 addr = evsel__intval(evsel, sample, "lock_addr");
+
+ if (show_thread_stats)
+ addr = sample->tid;
+
+ ls = lock_stat_findnew(addr, "No name");
+ if (!ls)
+ return -ENOMEM;
+
+ ts = thread_stat_findnew(sample->tid);
+ if (!ts)
+ return -ENOMEM;
+
+ seq = get_seq(ts, addr);
+ if (!seq)
+ return -ENOMEM;
+
+ switch (seq->state) {
+ case SEQ_STATE_UNINITIALIZED:
+ goto end;
+ case SEQ_STATE_CONTENDED:
+ contended_term = sample->time - seq->prev_event_time;
+ ls->wait_time_total += contended_term;
+ if (contended_term < ls->wait_time_min)
+ ls->wait_time_min = contended_term;
+ if (ls->wait_time_max < contended_term)
+ ls->wait_time_max = contended_term;
+ break;
+ case SEQ_STATE_ACQUIRING:
+ case SEQ_STATE_ACQUIRED:
+ case SEQ_STATE_READ_ACQUIRED:
+ case SEQ_STATE_RELEASED:
+ /* broken lock sequence */
+ if (!ls->broken) {
+ ls->broken = 1;
+ bad_hist[BROKEN_CONTENDED]++;
+ }
+ list_del_init(&seq->list);
+ free(seq);
+ goto end;
+ default:
+ BUG_ON("Unknown state of lock sequence found!\n");
+ break;
+ }
+
+ seq->state = SEQ_STATE_ACQUIRED;
+ ls->nr_acquired++;
+ ls->avg_wait_time = ls->wait_time_total/ls->nr_acquired;
+end:
+ return 0;
+}
+
/* lock oriented handlers */
/* TODO: handlers for CPU oriented, thread oriented */
static struct trace_lock_handler report_lock_ops = {
@@ -832,6 +950,8 @@ static struct trace_lock_handler report_lock_ops = {
.acquired_event = report_lock_acquired_event,
.contended_event = report_lock_contended_event,
.release_event = report_lock_release_event,
+ .contention_begin_event = report_lock_contention_begin_event,
+ .contention_end_event = report_lock_contention_end_event,
};

static struct trace_lock_handler *trace_handler;
@@ -1124,6 +1244,11 @@ static int __cmd_report(bool display_info)
goto out_delete;
}

+ if (perf_session__set_tracepoints_handlers(session, contention_tracepoints)) {
+ pr_err("Initializing perf session tracepoint handlers failed\n");
+ goto out_delete;
+ }
+
if (setup_output_field(output_fields))
goto out_delete;

--
2.36.1.255.ge46751e96f-goog
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