# Release 4.7 lib/flex_proportions.c

Directory: lib
/*
*  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 maintaining 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; }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 50 90.91% 1 33.33% tejun heo tejun heo 5 9.09% 2 66.67% Total 55 100.00% 3 100.00%

void fprop_global_destroy(struct fprop_global *p) { percpu_counter_destroy(&p->events); }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 18 100.00% 1 100.00% Total 18 100.00% 1 100.00%

/* * 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; }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 106 100.00% 3 100.00% Total 106 100.00% 3 100.00%

/* * ---- 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; }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 33 100.00% 1 100.00% Total 33 100.00% 1 100.00%

void fprop_local_destroy_single(struct fprop_local_single *pl) { }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 9 100.00% 1 100.00% Total 9 100.00% 1 100.00%

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); }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 114 100.00% 1 100.00% Total 114 100.00% 1 100.00%

/* 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); }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 37 100.00% 1 100.00% Total 37 100.00% 1 100.00%

/* 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; }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 115 100.00% 1 100.00% Total 115 100.00% 1 100.00%

/* * ---- 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; }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 49 90.74% 1 33.33% tejun heo tejun heo 5 9.26% 2 66.67% Total 54 100.00% 3 100.00%

void fprop_local_destroy_percpu(struct fprop_local_percpu *pl) { percpu_counter_destroy(&pl->events); }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 18 100.00% 1 100.00% Total 18 100.00% 1 100.00%

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); }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 166 100.00% 1 100.00% Total 166 100.00% 1 100.00%

/* 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); }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 44 100.00% 1 100.00% Total 44 100.00% 1 100.00%

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; }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 119 100.00% 1 100.00% Total 119 100.00% 1 100.00%

/* * 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); }

#### Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 96 100.00% 1 100.00% Total 96 100.00% 1 100.00%

#### Overall Contributors

 Person Tokens Prop Commits CommitProp jan kara jan kara 988 98.90% 3 50.00% tejun heo tejun heo 10 1.00% 2 33.33% bogdan sikora bogdan sikora 1 0.10% 1 16.67% Total 999 100.00% 6 100.00%
Directory: lib
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