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1/* SPDX-License-Identifier: GPL-2.0 */2/*3 * bch2_time_stats - collect statistics on events that have a duration, with nicely4 * formatted textual output on demand5 *6 * - percpu buffering of event collection: cheap enough to shotgun7 * everywhere without worrying about overhead8 *9 * tracks:10 * - number of events11 * - maximum event duration ever seen12 * - sum of all event durations13 * - average event duration, standard and weighted14 * - standard deviation of event durations, standard and weighted15 * and analagous statistics for the frequency of events16 *17 * We provide both mean and weighted mean (exponentially weighted), and standard18 * deviation and weighted standard deviation, to give an efficient-to-compute19 * view of current behaviour versus. average behaviour - "did this event source20 * just become wonky, or is this typical?".21 *22 * Particularly useful for tracking down latency issues.23 */24#ifndef _BCACHEFS_TIME_STATS_H25#define _BCACHEFS_TIME_STATS_H26 27#include <linux/sched/clock.h>28#include <linux/spinlock_types.h>29#include <linux/string.h>30 31#include "mean_and_variance.h"32 33struct time_unit {34 const char *name;35 u64 nsecs;36};37 38/*39 * given a nanosecond value, pick the preferred time units for printing:40 */41const struct time_unit *bch2_pick_time_units(u64 ns);42 43/*44 * quantiles - do not use:45 *46 * Only enabled if bch2_time_stats->quantiles_enabled has been manually set - don't47 * use in new code.48 */49 50#define NR_QUANTILES 1551#define QUANTILE_IDX(i) inorder_to_eytzinger0(i, NR_QUANTILES)52#define QUANTILE_FIRST eytzinger0_first(NR_QUANTILES)53#define QUANTILE_LAST eytzinger0_last(NR_QUANTILES)54 55struct quantiles {56 struct quantile_entry {57 u64 m;58 u64 step;59 } entries[NR_QUANTILES];60};61 62struct time_stat_buffer {63 unsigned nr;64 struct time_stat_buffer_entry {65 u64 start;66 u64 end;67 } entries[31];68};69 70struct bch2_time_stats {71 spinlock_t lock;72 bool have_quantiles;73 struct time_stat_buffer __percpu *buffer;74 /* all fields are in nanoseconds */75 u64 min_duration;76 u64 max_duration;77 u64 total_duration;78 u64 max_freq;79 u64 min_freq;80 u64 last_event;81 u64 last_event_start;82 83 struct mean_and_variance duration_stats;84 struct mean_and_variance freq_stats;85 86/* default weight for weighted mean and variance calculations */87#define TIME_STATS_MV_WEIGHT 888 89 struct mean_and_variance_weighted duration_stats_weighted;90 struct mean_and_variance_weighted freq_stats_weighted;91};92 93struct bch2_time_stats_quantiles {94 struct bch2_time_stats stats;95 struct quantiles quantiles;96};97 98static inline struct quantiles *time_stats_to_quantiles(struct bch2_time_stats *stats)99{100 return stats->have_quantiles101 ? &container_of(stats, struct bch2_time_stats_quantiles, stats)->quantiles102 : NULL;103}104 105void __bch2_time_stats_clear_buffer(struct bch2_time_stats *, struct time_stat_buffer *);106void __bch2_time_stats_update(struct bch2_time_stats *stats, u64, u64);107 108/**109 * time_stats_update - collect a new event being tracked110 *111 * @stats - bch2_time_stats to update112 * @start - start time of event, recorded with local_clock()113 *114 * The end duration of the event will be the current time115 */116static inline void bch2_time_stats_update(struct bch2_time_stats *stats, u64 start)117{118 __bch2_time_stats_update(stats, start, local_clock());119}120 121/**122 * track_event_change - track state change events123 *124 * @stats - bch2_time_stats to update125 * @v - new state, true or false126 *127 * Use this when tracking time stats for state changes, i.e. resource X becoming128 * blocked/unblocked.129 */130static inline bool track_event_change(struct bch2_time_stats *stats, bool v)131{132 if (v != !!stats->last_event_start) {133 if (!v) {134 bch2_time_stats_update(stats, stats->last_event_start);135 stats->last_event_start = 0;136 } else {137 stats->last_event_start = local_clock() ?: 1;138 return true;139 }140 }141 142 return false;143}144 145void bch2_time_stats_reset(struct bch2_time_stats *);146void bch2_time_stats_exit(struct bch2_time_stats *);147void bch2_time_stats_init(struct bch2_time_stats *);148 149static inline void bch2_time_stats_quantiles_exit(struct bch2_time_stats_quantiles *statq)150{151 bch2_time_stats_exit(&statq->stats);152}153static inline void bch2_time_stats_quantiles_init(struct bch2_time_stats_quantiles *statq)154{155 bch2_time_stats_init(&statq->stats);156 statq->stats.have_quantiles = true;157 memset(&statq->quantiles, 0, sizeof(statq->quantiles));158}159 160#endif /* _BCACHEFS_TIME_STATS_H */161