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
  16 struct 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  */
  37 struct prop_descriptor {
  38         int index;
  39         struct prop_global pg[2];
  40         struct mutex mutex;             /* serialize the prop_global switch */
  41 };
  42
  43 int prop_descriptor_init(struct prop_descriptor *pd, int shift);
  44 void prop_change_shift(struct prop_descriptor *pd, int new_shift);
  45
  46 /*
  47  * ----- PERCPU ------
  48  */
  49
  50 struct 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
  64 int prop_local_init_percpu(struct prop_local_percpu *pl);
  65 void prop_local_destroy_percpu(struct prop_local_percpu *pl);
  66 void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl);
  67 void prop_fraction_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl,
  68                 long *numerator, long *denominator);
  69
  70 static inline
  71 void 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
  93 void __prop_inc_percpu_max(struct prop_descriptor *pd,
  94                            struct prop_local_percpu *pl, long frac);
  95
  96
  97 /*
  98  * ----- SINGLE ------
  99  */
 100
 101 struct 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
 120 int prop_local_init_single(struct prop_local_single *pl);
 121 void prop_local_destroy_single(struct prop_local_single *pl);
 122 void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
 123 void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
 124                 long *numerator, long *denominator);
 125
 126 static inline
 127 void 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 */