bcachefs: mean_and_variance: put struct mean_and_variance_weighted on a diet

The only caller of this code (time_stats) always knows the weights and
whether or not any information has been collected.  Pass this
information into the mean and variance code so that it doesn't have to
store that information.  This reduces the structure size from 24 to 16
bytes, which shrinks each time_stats counter to 192 bytes from 208.

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

1 files changed, 6 insertions, 9 deletions

diff --git a/fs/bcachefs/time_stats.c b/fs/bcachefs/time_stats.c
index af97474c445b..4ac6ebfd264c 100644
--- a/fs/bcachefs/time_stats.c
+++ b/fs/bcachefs/time_stats.c
@@ -70,11 +70,13 @@ static inline void time_stats_update_one(struct bch2_time_stats *stats,
 					      u64 start, u64 end)
 {
 	u64 duration, freq;
+	bool initted = stats->last_event != 0;
 
 	if (time_after64(end, start)) {
 		duration = end - start;
 		mean_and_variance_update(&stats->duration_stats, duration);
-		mean_and_variance_weighted_update(&stats->duration_stats_weighted, duration);
+		mean_and_variance_weighted_update(&stats->duration_stats_weighted,
+				duration, initted, TIME_STATS_MV_WEIGHT);
 		stats->max_duration = max(stats->max_duration, duration);
 		stats->min_duration = min(stats->min_duration, duration);
 		stats->total_duration += duration;
@@ -86,7 +88,8 @@ static inline void time_stats_update_one(struct bch2_time_stats *stats,
 	if (stats->last_event && time_after64(end, stats->last_event)) {
 		freq = end - stats->last_event;
 		mean_and_variance_update(&stats->freq_stats, freq);
-		mean_and_variance_weighted_update(&stats->freq_stats_weighted, freq);
+		mean_and_variance_weighted_update(&stats->freq_stats_weighted,
+				freq, initted, TIME_STATS_MV_WEIGHT);
 		stats->max_freq = max(stats->max_freq, freq);
 		stats->min_freq = min(stats->min_freq, freq);
 	}
@@ -118,15 +121,11 @@ void __bch2_time_stats_update(struct bch2_time_stats *stats, u64 start, u64 end)
 {
 	unsigned long flags;
 
-	WARN_ONCE(!stats->duration_stats_weighted.weight ||
-		  !stats->freq_stats_weighted.weight,
-		  "uninitialized bch2_time_stats");
-
 	if (!stats->buffer) {
 		spin_lock_irqsave(&stats->lock, flags);
 		time_stats_update_one(stats, start, end);
 
-		if (mean_and_variance_weighted_get_mean(stats->freq_stats_weighted) < 32 &&
+		if (mean_and_variance_weighted_get_mean(stats->freq_stats_weighted, TIME_STATS_MV_WEIGHT) < 32 &&
 		    stats->duration_stats.n > 1024)
 			stats->buffer =
 				alloc_percpu_gfp(struct time_stat_buffer,
@@ -158,8 +157,6 @@ void bch2_time_stats_exit(struct bch2_time_stats *stats)
 void bch2_time_stats_init(struct bch2_time_stats *stats)
 {
 	memset(stats, 0, sizeof(*stats));
-	stats->duration_stats_weighted.weight = 8;
-	stats->freq_stats_weighted.weight = 8;
 	stats->min_duration = U64_MAX;
 	stats->min_freq = U64_MAX;
 	spin_lock_init(&stats->lock);