[PATCH 05/10] time_stats: don't print any output if event count is zero

[Darrick J. Wong]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

There's no point in printing an empty report for no data, so add a flag
that allows us to do that.

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
---
 include/linux/time_stats.h |    4 +++-
 lib/time_stats.c           |   10 ++++++----
 2 files changed, 9 insertions(+), 5 deletions(-)


diff --git a/include/linux/time_stats.h b/include/linux/time_stats.h
index 1c1ba8efa7bfe..994823c17bca9 100644
--- a/include/linux/time_stats.h
+++ b/include/linux/time_stats.h
@@ -148,8 +148,10 @@ static inline bool track_event_change(struct time_stats *stats, bool v)
 	return false;
 }
 
+#define TIME_STATS_PRINT_NO_ZEROES	(1U << 0)	/* print nothing if zero count */
 struct seq_buf;
-void time_stats_to_seq_buf(struct seq_buf *, struct time_stats *);
+void time_stats_to_seq_buf(struct seq_buf *, struct time_stats *,
+		unsigned int flags);
 
 void time_stats_exit(struct time_stats *);
 void time_stats_init(struct time_stats *);
diff --git a/lib/time_stats.c b/lib/time_stats.c
index 43106bda43a92..382935979f8f7 100644
--- a/lib/time_stats.c
+++ b/lib/time_stats.c
@@ -168,7 +168,8 @@ static inline u64 time_stats_lifetime(const struct time_stats *stats)
 	return local_clock() - (stats->start_time & ~TIME_STATS_HAVE_QUANTILES);
 }
 
-void time_stats_to_seq_buf(struct seq_buf *out, struct time_stats *stats)
+void time_stats_to_seq_buf(struct seq_buf *out, struct time_stats *stats,
+		unsigned int flags)
 {
 	struct quantiles *quantiles = time_stats_to_quantiles(stats);
 	s64 f_mean = 0, d_mean = 0;
@@ -184,14 +185,15 @@ void time_stats_to_seq_buf(struct seq_buf *out, struct time_stats *stats)
 		spin_unlock_irq(&stats->lock);
 	}
 
-	/*
-	 * avoid divide by zero
-	 */
 	if (stats->freq_stats.n) {
+		/* avoid divide by zero */
 		f_mean = mean_and_variance_get_mean(stats->freq_stats);
 		f_stddev = mean_and_variance_get_stddev(stats->freq_stats);
 		d_mean = mean_and_variance_get_mean(stats->duration_stats);
 		d_stddev = mean_and_variance_get_stddev(stats->duration_stats);
+	} else if (flags & TIME_STATS_PRINT_NO_ZEROES) {
+		/* unless we didn't want zeroes anyway */
+		return;
 	}
 
 	seq_buf_printf(out, "count: %llu\n", stats->duration_stats.n);