Update bcachefs sources to 50847e296b34 bcachefs: Check subvol <-> inode pointers...

[bcachefs-tools-debian] / include / linux / time_stats.h

diff --git a/include/linux/time_stats.h b/include/linux/time_stats.h
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+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * time_stats - collect statistics on events that have a duration, with nicely
+ * formatted textual output on demand
+ *
+ * - percpu buffering of event collection: cheap enough to shotgun
+ *   everywhere without worrying about overhead
+ *
+ * tracks:
+ *  - number of events
+ *  - maximum event duration ever seen
+ *  - sum of all event durations
+ *  - average event duration, standard and weighted
+ *  - standard deviation of event durations, standard and weighted
+ * and analagous statistics for the frequency of events
+ *
+ * We provide both mean and weighted mean (exponentially weighted), and standard
+ * deviation and weighted standard deviation, to give an efficient-to-compute
+ * view of current behaviour versus. average behaviour - "did this event source
+ * just become wonky, or is this typical?".
+ *
+ * Particularly useful for tracking down latency issues.
+ */
+#ifndef _LINUX_TIME_STATS_H
+#define _LINUX_TIME_STATS_H
+
+#include <linux/mean_and_variance.h>
+#include <linux/sched/clock.h>
+#include <linux/spinlock_types.h>
+#include <linux/string.h>
+
+struct time_unit {
+       const char      *name;
+       u64             nsecs;
+};
+
+/*
+ * given a nanosecond value, pick the preferred time units for printing:
+ */
+const struct time_unit *pick_time_units(u64 ns);
+
+/*
+ * quantiles - do not use:
+ *
+ * Only enabled if time_stats->quantiles_enabled has been manually set - don't
+ * use in new code.
+ */
+
+#define NR_QUANTILES   15
+#define QUANTILE_IDX(i)        inorder_to_eytzinger0(i, NR_QUANTILES)
+#define QUANTILE_FIRST eytzinger0_first(NR_QUANTILES)
+#define QUANTILE_LAST  eytzinger0_last(NR_QUANTILES)
+
+struct quantiles {
+       struct quantile_entry {
+               u64     m;
+               u64     step;
+       }               entries[NR_QUANTILES];
+};
+
+struct time_stat_buffer {
+       unsigned        nr;
+       struct time_stat_buffer_entry {
+               u64     start;
+               u64     end;
+       }               entries[31];
+};
+
+struct time_stats {
+       spinlock_t      lock;
+       bool            have_quantiles;
+       /* all fields are in nanoseconds */
+       u64             min_duration;
+       u64             max_duration;
+       u64             total_duration;
+       u64             max_freq;
+       u64             min_freq;
+       u64             last_event;
+       u64             last_event_start;
+
+       struct mean_and_variance          duration_stats;
+       struct mean_and_variance          freq_stats;
+
+/* default weight for weighted mean and variance calculations */
+#define TIME_STATS_MV_WEIGHT   8
+
+       struct mean_and_variance_weighted duration_stats_weighted;
+       struct mean_and_variance_weighted freq_stats_weighted;
+       struct time_stat_buffer __percpu *buffer;
+
+       u64             start_time;
+};
+
+struct time_stats_quantiles {
+       struct time_stats       stats;
+       struct quantiles        quantiles;
+};
+
+static inline struct quantiles *time_stats_to_quantiles(struct time_stats *stats)
+{
+       return stats->have_quantiles
+               ? &container_of(stats, struct time_stats_quantiles, stats)->quantiles
+               : NULL;
+}
+
+void __time_stats_clear_buffer(struct time_stats *, struct time_stat_buffer *);
+void __time_stats_update(struct time_stats *stats, u64, u64);
+
+/**
+ * time_stats_update - collect a new event being tracked
+ *
+ * @stats      - time_stats to update
+ * @start      - start time of event, recorded with local_clock()
+ *
+ * The end duration of the event will be the current time
+ */
+static inline void time_stats_update(struct time_stats *stats, u64 start)
+{
+       __time_stats_update(stats, start, local_clock());
+}
+
+/**
+ * track_event_change - track state change events
+ *
+ * @stats      - time_stats to update
+ * @v          - new state, true or false
+ *
+ * Use this when tracking time stats for state changes, i.e. resource X becoming
+ * blocked/unblocked.
+ */
+static inline bool track_event_change(struct time_stats *stats, bool v)
+{
+       if (v != !!stats->last_event_start) {
+               if (!v) {
+                       time_stats_update(stats, stats->last_event_start);
+                       stats->last_event_start = 0;
+               } else {
+                       stats->last_event_start = local_clock() ?: 1;
+                       return true;
+               }
+       }
+
+       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 *,
+               const char *epoch_name, unsigned int flags);
+void time_stats_to_json(struct seq_buf *, struct time_stats *,
+               const char *epoch_name, unsigned int flags);
+
+void time_stats_exit(struct time_stats *);
+void time_stats_init(struct time_stats *);
+
+static inline void time_stats_quantiles_exit(struct time_stats_quantiles *statq)
+{
+       time_stats_exit(&statq->stats);
+}
+static inline void time_stats_quantiles_init(struct time_stats_quantiles *statq)
+{
+       time_stats_init(&statq->stats);
+       statq->stats.have_quantiles = true;
+       memset(&statq->quantiles, 0, sizeof(statq->quantiles));
+}
+
+#endif /* _LINUX_TIME_STATS_H */