LXR linux/include/linux/proportions.h

   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        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#define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
  85
  86#define PROP_FRAC_SHIFT         (BITS_PER_LONG - PROP_MAX_SHIFT - 1)
  87#define PROP_FRAC_BASE          (1UL << PROP_FRAC_SHIFT)
  88
  89void __prop_inc_percpu_max(struct prop_descriptor *pd,
  90                           struct prop_local_percpu *pl, long frac);
  91
  92
  93/*
  94 * ----- SINGLE ------
  95 */
  96
  97struct prop_local_single {
  98        /*
  99         * the local events counter
 100         */
 101        unsigned long events;
 102
 103        /*
 104         * snapshot of the last seen global state
 105         * and a lock protecting this state
 106         */
 107        unsigned long period;
 108        int shift;
 109        spinlock_t lock;                /* protect the snapshot state */
 110};
 111
 112#define INIT_PROP_LOCAL_SINGLE(name)                    \
 113{       .lock = __SPIN_LOCK_UNLOCKED(name.lock),        \
 114}
 115
 116int prop_local_init_single(struct prop_local_single *pl);
 117void prop_local_destroy_single(struct prop_local_single *pl);
 118void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
 119void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
 120                long *numerator, long *denominator);
 121
 122static inline
 123void prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
 124{
 125        unsigned long flags;
 126
 127        local_irq_save(flags);
 128        __prop_inc_single(pd, pl);
 129        local_irq_restore(flags);
 130}
 131
 132#endif /* _LINUX_PROPORTIONS_H */
 133