[PATCH 7/7] perf lock: account for lock average wait time

[Davidlohr Bueso <davidlohr@hp.com>]

While perf-lock currently reports both the total wait time
and the number of contentions, it doesn't explicitly show
the average wait time. Having this value immediately in the
report can be quite useful when looking into performance issues.

Furthermore, allowing report to sort by averages is another
handy feature to have - and thus do not only print the value, but
add it to the lock_stat structure.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
---
 tools/perf/Documentation/perf-lock.txt |  2 +-
 tools/perf/builtin-lock.c              | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
index c7f5f55..ab25be2 100644
--- a/tools/perf/Documentation/perf-lock.txt
+++ b/tools/perf/Documentation/perf-lock.txt
@@ -48,7 +48,7 @@ REPORT OPTIONS
 -k::
 --key=<value>::
         Sorting key. Possible values: acquired (default), contended,
-        wait_total, wait_max, wait_min.
+	avg_wait, wait_total, wait_max, wait_min.
 
 INFO OPTIONS
 ------------
diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 5adebe6..f0a5871 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -56,7 +56,9 @@ struct lock_stat {
 
 	unsigned int		nr_readlock;
 	unsigned int		nr_trylock;
+
 	/* these times are in nano sec. */
+	u64                     avg_wait_time;
 	u64			wait_time_total;
 	u64			wait_time_min;
 	u64			wait_time_max;
@@ -208,6 +210,7 @@ static struct thread_stat *thread_stat_findnew_first(u32 tid)
 
 SINGLE_KEY(nr_acquired)
 SINGLE_KEY(nr_contended)
+SINGLE_KEY(avg_wait_time)
 SINGLE_KEY(wait_time_total)
 SINGLE_KEY(wait_time_max)
 
@@ -244,6 +247,7 @@ static struct rb_root		result;	/* place to store sorted data */
 struct lock_key keys[] = {
 	DEF_KEY_LOCK(acquired, nr_acquired),
 	DEF_KEY_LOCK(contended, nr_contended),
+	DEF_KEY_LOCK(avg_wait, avg_wait_time),
 	DEF_KEY_LOCK(wait_total, wait_time_total),
 	DEF_KEY_LOCK(wait_min, wait_time_min),
 	DEF_KEY_LOCK(wait_max, wait_time_max),
@@ -516,6 +520,7 @@ static int report_lock_acquired_event(struct perf_evsel *evsel,
 
 	seq->state = SEQ_STATE_ACQUIRED;
 	ls->nr_acquired++;
+	ls->avg_wait_time = ls->nr_contended ? ls->wait_time_total/ls->nr_contended : 0;
 	seq->prev_event_time = sample->time;
 end:
 	return 0;
@@ -570,6 +575,7 @@ static int report_lock_contended_event(struct perf_evsel *evsel,
 
 	seq->state = SEQ_STATE_CONTENDED;
 	ls->nr_contended++;
+	ls->avg_wait_time = ls->wait_time_total/ls->nr_contended;
 	seq->prev_event_time = sample->time;
 end:
 	return 0;
@@ -702,6 +708,7 @@ static void print_result(void)
 	pr_info("%10s ", "acquired");
 	pr_info("%10s ", "contended");
 
+	pr_info("%15s ", "avg wait (ns)");
 	pr_info("%15s ", "total wait (ns)");
 	pr_info("%15s ", "max wait (ns)");
 	pr_info("%15s ", "min wait (ns)");
@@ -720,6 +727,7 @@ static void print_result(void)
 		pr_info("%10u ", st->nr_acquired);
 		pr_info("%10u ", st->nr_contended);
 
+		pr_info("%15" PRIu64 " ", st->avg_wait_time);
 		pr_info("%15" PRIu64 " ", st->wait_time_total);
 		pr_info("%15" PRIu64 " ", st->wait_time_max);
 		pr_info("%15" PRIu64 " ", st->wait_time_min == ULLONG_MAX ?
@@ -926,7 +934,7 @@ int cmd_lock(int argc, const char **argv, const char *prefix __maybe_unused)
 	};
 	const struct option report_options[] = {
 	OPT_STRING('k', "key", &sort_key, "acquired",
-		    "key for sorting (acquired / contended / wait_total / wait_max / wait_min)"),
+		    "key for sorting (acquired / contended / avg_wait / wait_total / wait_max / wait_min)"),
 	/* TODO: type */
 	OPT_END()
 	};
-- 
1.7.11.7