bcachefs: time_stats: Check for last_event == 0 when updating freq stats

Kent Overstreet · Kent Overstreet · commit 7b508b323b2e · 2024-02-05T01:16:31.000-05:00
This fixes spurious outliers in the frequency stats.

Signed-off-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
diff --git a/fs/bcachefs/util.c b/fs/bcachefs/util.c
@@ -418,14 +418,15 @@ static inline void bch2_time_stats_update_one(struct bch2_time_stats *stats,
 		bch2_quantiles_update(&stats->quantiles, duration);
 	}
 
-	if (time_after64(end, stats->last_event)) {
+	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);
 		stats->max_freq = max(stats->max_freq, freq);
 		stats->min_freq = min(stats->min_freq, freq);
-		stats->last_event = end;
 	}
+
+	stats->last_event = end;
 }
 
 static void __bch2_time_stats_clear_buffer(struct bch2_time_stats *stats,

Original file line number	Diff line number	Diff line change
`@@ -418,14 +418,15 @@ static inline void bch2_time_stats_update_one(struct bch2_time_stats *stats,`
`418`	`418`	`bch2_quantiles_update(&stats->quantiles, duration);`
`419`	`419`	`}`
`420`	`420`
`421`		`- if (time_after64(end, stats->last_event)) {`
	`421`	`+ if (stats->last_event && time_after64(end, stats->last_event)) {`
`422`	`422`	`freq = end - stats->last_event;`
`423`	`423`	`mean_and_variance_update(&stats->freq_stats, freq);`
`424`	`424`	`mean_and_variance_weighted_update(&stats->freq_stats_weighted, freq);`
`425`	`425`	`stats->max_freq = max(stats->max_freq, freq);`
`426`	`426`	`stats->min_freq = min(stats->min_freq, freq);`
`427`		`- stats->last_event = end;`
`428`	`427`	`}`
	`428`	`+`
	`429`	`+ stats->last_event = end;`
`429`	`430`	`}`
`430`	`431`
`431`	`432`	`static void __bch2_time_stats_clear_buffer(struct bch2_time_stats *stats,`