linux/include/linux/proportions.h
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   1/*
   2 * FLoating proportions
   3 *
   4 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
   5 *
   6 * This file contains the public data structure and API definitions.
   7 */
   8
   9#ifndef _LINUX_PROPORTIONS_H
  10#define _LINUX_PROPORTIONS_H
  11
  12#include <linux/percpu_counter.h>
  13#include <linux/spinlock.h>
  14#include <linux/mutex.h>
  15
  16struct prop_global {
  17        /*
  18         * The period over which we differentiate
  19         *
  20         *   period = 2^shift
  21         */
  22        int shift;
  23        /*
  24         * The total event counter aka 'time'.
  25         *
  26         * Treated as an unsigned long; the lower 'shift - 1' bits are the
  27         * counter bits, the remaining upper bits the period counter.
  28         */
  29        struct percpu_counter events;
  30};
  31
  32/*
  33 * global proportion descriptor
  34 *
  35 * this is needed to consitently flip prop_global structures.
  36 */
  37struct prop_descriptor {
  38        int index;
  39        struct prop_global pg[2];
  40        struct mutex mutex;             /* serialize the prop_global switch */
  41};
  42
  43int prop_descriptor_init(struct prop_descriptor *pd, int shift);
  44void prop_change_shift(struct prop_descriptor *pd, int new_shift);
  45
  46/*
  47 * ----- PERCPU ------
  48 */
  49
  50struct prop_local_percpu {
  51        /*
  52         * the local events counter
  53         */
  54        struct percpu_counter events;
  55
  56        /*
  57         * snapshot of the last seen global state
  58         */
  59        int shift;
  60        unsigned long period;
  61        raw_spinlock_t lock;            /* protect the snapshot state */
  62};
  63
  64int prop_local_init_percpu(struct prop_local_percpu *pl);
  65void prop_local_destroy_percpu(struct prop_local_percpu *pl);
  66void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl);
  67void prop_fraction_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl,
  68                long *numerator, long *denominator);
  69
  70static inline
  71void prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
  72{
  73        unsigned long flags;
  74
  75        local_irq_save(flags);
  76        __prop_inc_percpu(pd, pl);
  77        local_irq_restore(flags);
  78}
  79
  80/*
  81 * Limit the time part in order to ensure there are some bits left for the
  82 * cycle counter and fraction multiply.
  83 */
  84#if BITS_PER_LONG == 32
  85#define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
  86#else
  87#define PROP_MAX_SHIFT (BITS_PER_LONG/2)
  88#endif
  89
  90#define PROP_FRAC_SHIFT         (BITS_PER_LONG - PROP_MAX_SHIFT - 1)
  91#define PROP_FRAC_BASE          (1UL << PROP_FRAC_SHIFT)
  92
  93void __prop_inc_percpu_max(struct prop_descriptor *pd,
  94                           struct prop_local_percpu *pl, long frac);
  95
  96
  97/*
  98 * ----- SINGLE ------
  99 */
 100
 101struct prop_local_single {
 102        /*
 103         * the local events counter
 104         */
 105        unsigned long events;
 106
 107        /*
 108         * snapshot of the last seen global state
 109         * and a lock protecting this state
 110         */
 111        unsigned long period;
 112        int shift;
 113        raw_spinlock_t lock;            /* protect the snapshot state */
 114};
 115
 116#define INIT_PROP_LOCAL_SINGLE(name)                    \
 117{       .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock),    \
 118}
 119
 120int prop_local_init_single(struct prop_local_single *pl);
 121void prop_local_destroy_single(struct prop_local_single *pl);
 122void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
 123void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
 124                long *numerator, long *denominator);
 125
 126static inline
 127void prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
 128{
 129        unsigned long flags;
 130
 131        local_irq_save(flags);
 132        __prop_inc_single(pd, pl);
 133        local_irq_restore(flags);
 134}
 135
 136#endif /* _LINUX_PROPORTIONS_H */
 137
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