bcachefs: pull out time_stats.[ch]

prep work for lifting out of fs/bcachefs/

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 163 insertions, 0 deletions

diff --git a/fs/bcachefs/time_stats.c b/fs/bcachefs/time_stats.c
new file mode 100644
index 000000000000..d2f7ddbf6c31
--- /dev/null
+++ b/fs/bcachefs/time_stats.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
+#include <linux/time.h>
+#include <linux/spinlock.h>
+
+#include "eytzinger.h"
+#include "time_stats.h"
+
+static const struct time_unit time_units[] = {
+	{ "ns",		1		 },
+	{ "us",		NSEC_PER_USEC	 },
+	{ "ms",		NSEC_PER_MSEC	 },
+	{ "s",		NSEC_PER_SEC	 },
+	{ "m",          (u64) NSEC_PER_SEC * 60},
+	{ "h",          (u64) NSEC_PER_SEC * 3600},
+	{ "eon",        U64_MAX          },
+};
+
+const struct time_unit *bch2_pick_time_units(u64 ns)
+{
+	const struct time_unit *u;
+
+	for (u = time_units;
+	     u + 1 < time_units + ARRAY_SIZE(time_units) &&
+	     ns >= u[1].nsecs << 1;
+	     u++)
+		;
+
+	return u;
+}
+
+static void quantiles_update(struct quantiles *q, u64 v)
+{
+	unsigned i = 0;
+
+	while (i < ARRAY_SIZE(q->entries)) {
+		struct quantile_entry *e = q->entries + i;
+
+		if (unlikely(!e->step)) {
+			e->m = v;
+			e->step = max_t(unsigned, v / 2, 1024);
+		} else if (e->m > v) {
+			e->m = e->m >= e->step
+				? e->m - e->step
+				: 0;
+		} else if (e->m < v) {
+			e->m = e->m + e->step > e->m
+				? e->m + e->step
+				: U32_MAX;
+		}
+
+		if ((e->m > v ? e->m - v : v - e->m) < e->step)
+			e->step = max_t(unsigned, e->step / 2, 1);
+
+		if (v >= e->m)
+			break;
+
+		i = eytzinger0_child(i, v > e->m);
+	}
+}
+
+static inline void time_stats_update_one(struct bch2_time_stats *stats,
+					      u64 start, u64 end)
+{
+	u64 duration, freq;
+
+	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);
+		stats->max_duration = max(stats->max_duration, duration);
+		stats->min_duration = min(stats->min_duration, duration);
+		stats->total_duration += duration;
+
+		if (stats->quantiles_enabled)
+			quantiles_update(&stats->quantiles, duration);
+	}
+
+	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;
+}
+
+void __bch2_time_stats_clear_buffer(struct bch2_time_stats *stats,
+				    struct time_stat_buffer *b)
+{
+	for (struct time_stat_buffer_entry *i = b->entries;
+	     i < b->entries + ARRAY_SIZE(b->entries);
+	     i++)
+		time_stats_update_one(stats, i->start, i->end);
+	b->nr = 0;
+}
+
+static noinline void time_stats_clear_buffer(struct bch2_time_stats *stats,
+					     struct time_stat_buffer *b)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&stats->lock, flags);
+	__bch2_time_stats_clear_buffer(stats, b);
+	spin_unlock_irqrestore(&stats->lock, flags);
+}
+
+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 &&
+		    stats->duration_stats.n > 1024)
+			stats->buffer =
+				alloc_percpu_gfp(struct time_stat_buffer,
+						 GFP_ATOMIC);
+		spin_unlock_irqrestore(&stats->lock, flags);
+	} else {
+		struct time_stat_buffer *b;
+
+		preempt_disable();
+		b = this_cpu_ptr(stats->buffer);
+
+		BUG_ON(b->nr >= ARRAY_SIZE(b->entries));
+		b->entries[b->nr++] = (struct time_stat_buffer_entry) {
+			.start = start,
+			.end = end
+		};
+
+		if (unlikely(b->nr == ARRAY_SIZE(b->entries)))
+			time_stats_clear_buffer(stats, b);
+		preempt_enable();
+	}
+}
+
+void bch2_time_stats_exit(struct bch2_time_stats *stats)
+{
+	free_percpu(stats->buffer);
+}
+
+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);
+}