[PATCH 5/7] perf lock: Handle lock contention tracepoints

[Namhyung Kim]

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@xxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/perf/builtin-lock.c | 137 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 9e3b90cac505..546dad1963c8 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -483,6 +483,18 @@ static struct lock_stat *pop_from_result(void)
 	return container_of(node, struct lock_stat, rb);
 }
 
+static struct lock_stat *lock_stat_find(u64 addr)
+{
+	struct hlist_head *entry = lockhashentry(addr);
+	struct lock_stat *ret;
+
+	hlist_for_each_entry(ret, entry, hash_entry) {
+		if (ret->addr == addr)
+			return ret;
+	}
+	return NULL;
+}
+
 static struct lock_stat *lock_stat_findnew(u64 addr, const char *name)
 {
 	struct hlist_head *entry = lockhashentry(addr);
@@ -827,6 +839,124 @@ 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_find(addr);
+	if (!ls)
+		return 0;
+
+	ts = thread_stat_find(sample->tid);
+	if (!ts)
+		return 0;
+
+	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_ACQUIRED]++;
+		}
+		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  = {
@@ -834,6 +964,8 @@ 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;
@@ -1126,6 +1258,11 @@ 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;
 
-- 
2.36.1.476.g0c4daa206d-goog