time_stats: report lifetime of the stats object

Capture the initialization time of the time_stats object so that we can
report how long the counter has been observing data.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

2 files changed, 11 insertions, 0 deletions

diff --git a/fs/bcachefs/time_stats.c b/fs/bcachefs/time_stats.c
index 232da8488060..b6184cc4106d 100644
--- a/fs/bcachefs/time_stats.c
+++ b/fs/bcachefs/time_stats.c
@@ -174,11 +174,17 @@ static void seq_buf_time_units_aligned(struct seq_buf *out, u64 ns)
 	seq_buf_printf(out, "%8llu %s", div64_u64(ns, u->nsecs), u->name);
 }
 
+static inline u64 time_stats_lifetime(const struct bch2_time_stats *stats)
+{
+	return local_clock() - stats->start_time;
+}
+
 void bch2_time_stats_to_seq_buf(struct seq_buf *out, struct bch2_time_stats *stats)
 {
 	struct quantiles *quantiles = time_stats_to_quantiles(stats);
 	s64 f_mean = 0, d_mean = 0;
 	u64 f_stddev = 0, d_stddev = 0;
+	u64 lifetime = time_stats_lifetime(stats);
 
 	if (stats->buffer) {
 		int cpu;
@@ -200,6 +206,9 @@ void bch2_time_stats_to_seq_buf(struct seq_buf *out, struct bch2_time_stats *sta
 	}
 
 	seq_buf_printf(out, "count: %llu\n", stats->duration_stats.n);
+	seq_buf_printf(out, "lifetime: ");
+	seq_buf_time_units_aligned(out, lifetime);
+	seq_buf_printf(out, "\n");
 
 	seq_buf_printf(out, "                       since mount        recent\n");
 
@@ -276,5 +285,6 @@ void bch2_time_stats_init(struct bch2_time_stats *stats)
 	memset(stats, 0, sizeof(*stats));
 	stats->min_duration = U64_MAX;
 	stats->min_freq = U64_MAX;
+	stats->start_time = local_clock();
 	spin_lock_init(&stats->lock);
 }
diff --git a/fs/bcachefs/time_stats.h b/fs/bcachefs/time_stats.h
index 51d7396d476b..3ef9c41128a2 100644
--- a/fs/bcachefs/time_stats.h
+++ b/fs/bcachefs/time_stats.h
@@ -79,6 +79,7 @@ struct bch2_time_stats {
 	u64             min_freq;
 	u64		last_event;
 	u64		last_event_start;
+	u64		start_time;
 
 	struct mean_and_variance	  duration_stats;
 	struct mean_and_variance	  freq_stats;