include/linux/proportions.h

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