123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272 |
- /*
- * Floating proportions with flexible aging period
- *
- * Copyright (C) 2011, SUSE, Jan Kara <jack@suse.cz>
- *
- * The goal of this code is: Given different types of event, measure proportion
- * of each type of event over time. The proportions are measured with
- * exponentially decaying history to give smooth transitions. A formula
- * expressing proportion of event of type 'j' is:
- *
- * p_{j} = (\Sum_{i>=0} x_{i,j}/2^{i+1})/(\Sum_{i>=0} x_i/2^{i+1})
- *
- * Where x_{i,j} is j's number of events in i-th last time period and x_i is
- * total number of events in i-th last time period.
- *
- * Note that p_{j}'s are normalised, i.e.
- *
- * \Sum_{j} p_{j} = 1,
- *
- * This formula can be straightforwardly computed by maintaing denominator
- * (let's call it 'd') and for each event type its numerator (let's call it
- * 'n_j'). When an event of type 'j' happens, we simply need to do:
- * n_j++; d++;
- *
- * When a new period is declared, we could do:
- * d /= 2
- * for each j
- * n_j /= 2
- *
- * To avoid iteration over all event types, we instead shift numerator of event
- * j lazily when someone asks for a proportion of event j or when event j
- * occurs. This can bit trivially implemented by remembering last period in
- * which something happened with proportion of type j.
- */
- #include <linux/flex_proportions.h>
- int fprop_global_init(struct fprop_global *p, gfp_t gfp)
- {
- int err;
- p->period = 0;
- /* Use 1 to avoid dealing with periods with 0 events... */
- err = percpu_counter_init(&p->events, 1, gfp);
- if (err)
- return err;
- seqcount_init(&p->sequence);
- return 0;
- }
- void fprop_global_destroy(struct fprop_global *p)
- {
- percpu_counter_destroy(&p->events);
- }
- /*
- * Declare @periods new periods. It is upto the caller to make sure period
- * transitions cannot happen in parallel.
- *
- * The function returns true if the proportions are still defined and false
- * if aging zeroed out all events. This can be used to detect whether declaring
- * further periods has any effect.
- */
- bool fprop_new_period(struct fprop_global *p, int periods)
- {
- s64 events;
- unsigned long flags;
- local_irq_save(flags);
- events = percpu_counter_sum(&p->events);
- /*
- * Don't do anything if there are no events.
- */
- if (events <= 1) {
- local_irq_restore(flags);
- return false;
- }
- write_seqcount_begin(&p->sequence);
- if (periods < 64)
- events -= events >> periods;
- /* Use addition to avoid losing events happening between sum and set */
- percpu_counter_add(&p->events, -events);
- p->period += periods;
- write_seqcount_end(&p->sequence);
- local_irq_restore(flags);
- return true;
- }
- /*
- * ---- SINGLE ----
- */
- int fprop_local_init_single(struct fprop_local_single *pl)
- {
- pl->events = 0;
- pl->period = 0;
- raw_spin_lock_init(&pl->lock);
- return 0;
- }
- void fprop_local_destroy_single(struct fprop_local_single *pl)
- {
- }
- static void fprop_reflect_period_single(struct fprop_global *p,
- struct fprop_local_single *pl)
- {
- unsigned int period = p->period;
- unsigned long flags;
- /* Fast path - period didn't change */
- if (pl->period == period)
- return;
- raw_spin_lock_irqsave(&pl->lock, flags);
- /* Someone updated pl->period while we were spinning? */
- if (pl->period >= period) {
- raw_spin_unlock_irqrestore(&pl->lock, flags);
- return;
- }
- /* Aging zeroed our fraction? */
- if (period - pl->period < BITS_PER_LONG)
- pl->events >>= period - pl->period;
- else
- pl->events = 0;
- pl->period = period;
- raw_spin_unlock_irqrestore(&pl->lock, flags);
- }
- /* Event of type pl happened */
- void __fprop_inc_single(struct fprop_global *p, struct fprop_local_single *pl)
- {
- fprop_reflect_period_single(p, pl);
- pl->events++;
- percpu_counter_add(&p->events, 1);
- }
- /* Return fraction of events of type pl */
- void fprop_fraction_single(struct fprop_global *p,
- struct fprop_local_single *pl,
- unsigned long *numerator, unsigned long *denominator)
- {
- unsigned int seq;
- s64 num, den;
- do {
- seq = read_seqcount_begin(&p->sequence);
- fprop_reflect_period_single(p, pl);
- num = pl->events;
- den = percpu_counter_read_positive(&p->events);
- } while (read_seqcount_retry(&p->sequence, seq));
- /*
- * Make fraction <= 1 and denominator > 0 even in presence of percpu
- * counter errors
- */
- if (den <= num) {
- if (num)
- den = num;
- else
- den = 1;
- }
- *denominator = den;
- *numerator = num;
- }
- /*
- * ---- PERCPU ----
- */
- #define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
- int fprop_local_init_percpu(struct fprop_local_percpu *pl, gfp_t gfp)
- {
- int err;
- err = percpu_counter_init(&pl->events, 0, gfp);
- if (err)
- return err;
- pl->period = 0;
- raw_spin_lock_init(&pl->lock);
- return 0;
- }
- void fprop_local_destroy_percpu(struct fprop_local_percpu *pl)
- {
- percpu_counter_destroy(&pl->events);
- }
- static void fprop_reflect_period_percpu(struct fprop_global *p,
- struct fprop_local_percpu *pl)
- {
- unsigned int period = p->period;
- unsigned long flags;
- /* Fast path - period didn't change */
- if (pl->period == period)
- return;
- raw_spin_lock_irqsave(&pl->lock, flags);
- /* Someone updated pl->period while we were spinning? */
- if (pl->period >= period) {
- raw_spin_unlock_irqrestore(&pl->lock, flags);
- return;
- }
- /* Aging zeroed our fraction? */
- if (period - pl->period < BITS_PER_LONG) {
- s64 val = percpu_counter_read(&pl->events);
- if (val < (nr_cpu_ids * PROP_BATCH))
- val = percpu_counter_sum(&pl->events);
- __percpu_counter_add(&pl->events,
- -val + (val >> (period-pl->period)), PROP_BATCH);
- } else
- percpu_counter_set(&pl->events, 0);
- pl->period = period;
- raw_spin_unlock_irqrestore(&pl->lock, flags);
- }
- /* Event of type pl happened */
- void __fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl)
- {
- fprop_reflect_period_percpu(p, pl);
- __percpu_counter_add(&pl->events, 1, PROP_BATCH);
- percpu_counter_add(&p->events, 1);
- }
- void fprop_fraction_percpu(struct fprop_global *p,
- struct fprop_local_percpu *pl,
- unsigned long *numerator, unsigned long *denominator)
- {
- unsigned int seq;
- s64 num, den;
- do {
- seq = read_seqcount_begin(&p->sequence);
- fprop_reflect_period_percpu(p, pl);
- num = percpu_counter_read_positive(&pl->events);
- den = percpu_counter_read_positive(&p->events);
- } while (read_seqcount_retry(&p->sequence, seq));
- /*
- * Make fraction <= 1 and denominator > 0 even in presence of percpu
- * counter errors
- */
- if (den <= num) {
- if (num)
- den = num;
- else
- den = 1;
- }
- *denominator = den;
- *numerator = num;
- }
- /*
- * Like __fprop_inc_percpu() except that event is counted only if the given
- * type has fraction smaller than @max_frac/FPROP_FRAC_BASE
- */
- void __fprop_inc_percpu_max(struct fprop_global *p,
- struct fprop_local_percpu *pl, int max_frac)
- {
- if (unlikely(max_frac < FPROP_FRAC_BASE)) {
- unsigned long numerator, denominator;
- fprop_fraction_percpu(p, pl, &numerator, &denominator);
- if (numerator >
- (((u64)denominator) * max_frac) >> FPROP_FRAC_SHIFT)
- return;
- } else
- fprop_reflect_period_percpu(p, pl);
- __percpu_counter_add(&pl->events, 1, PROP_BATCH);
- percpu_counter_add(&p->events, 1);
- }
|