include/linux/percpu_counter.h

   1 #ifndef _LINUX_PERCPU_COUNTER_H
   2 #define _LINUX_PERCPU_COUNTER_H
   3 /*
   4  * A simple "approximate counter" for use in ext2 and ext3 superblocks.
   5  *
   6  * WARNING: these things are HUGE.  4 kbytes per counter on 32-way P4.
   7  */
   8
   9 #include <linux/spinlock.h>
  10 #include <linux/smp.h>
  11 #include <linux/list.h>
  12 #include <linux/threads.h>
  13 #include <linux/percpu.h>
  14 #include <linux/types.h>
  15
  16 #ifdef CONFIG_SMP
  17
  18 struct percpu_counter {
  19         spinlock_t lock;
  20         s64 count;
  21 #ifdef CONFIG_HOTPLUG_CPU
  22         struct list_head list;  /* All percpu_counters are on a list */
  23 #endif
  24         s32 *counters;
  25 };
  26
  27 #if NR_CPUS >= 16
  28 #define FBC_BATCH       (NR_CPUS*2)
  29 #else
  30 #define FBC_BATCH       (NR_CPUS*4)
  31 #endif
  32
  33 int percpu_counter_init(struct percpu_counter *fbc, s64 amount);
  34 int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount);
  35 void percpu_counter_destroy(struct percpu_counter *fbc);
  36 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
  37 void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
  38 s64 __percpu_counter_sum(struct percpu_counter *fbc, int set);
  39
  40 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
  41 {
  42         __percpu_counter_add(fbc, amount, FBC_BATCH);
  43 }
  44
  45 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
  46 {
  47         s64 ret = __percpu_counter_sum(fbc, 0);
  48         return ret < 0 ? 0 : ret;
  49 }
  50
  51 static inline s64 percpu_counter_sum_and_set(struct percpu_counter *fbc)
  52 {
  53         return __percpu_counter_sum(fbc, 1);
  54 }
  55
  56
  57 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
  58 {
  59         return __percpu_counter_sum(fbc, 0);
  60 }
  61
  62 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
  63 {
  64         return fbc->count;
  65 }
  66
  67 /*
  68  * It is possible for the percpu_counter_read() to return a small negative
  69  * number for some counter which should never be negative.
  70  *
  71  */
  72 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
  73 {
  74         s64 ret = fbc->count;
  75
  76         barrier();              /* Prevent reloads of fbc->count */
  77         if (ret >= 0)
  78                 return ret;
  79         return 1;
  80 }
  81
  82 #else
  83
  84 struct percpu_counter {
  85         s64 count;
  86 };
  87
  88 static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
  89 {
  90         fbc->count = amount;
  91         return 0;
  92 }
  93
  94 #define percpu_counter_init_irq percpu_counter_init
  95
  96 static inline void percpu_counter_destroy(struct percpu_counter *fbc)
  97 {
  98 }
  99
 100 static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
 101 {
 102         fbc->count = amount;
 103 }
 104
 105 #define __percpu_counter_add(fbc, amount, batch) \
 106         percpu_counter_add(fbc, amount)
 107
 108 static inline void
 109 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
 110 {
 111         preempt_disable();
 112         fbc->count += amount;
 113         preempt_enable();
 114 }
 115
 116 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
 117 {
 118         return fbc->count;
 119 }
 120
 121 static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
 122 {
 123         return fbc->count;
 124 }
 125
 126 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
 127 {
 128         return percpu_counter_read_positive(fbc);
 129 }
 130
 131 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
 132 {
 133         return percpu_counter_read(fbc);
 134 }
 135
 136 #endif  /* CONFIG_SMP */
 137
 138 static inline void percpu_counter_inc(struct percpu_counter *fbc)
 139 {
 140         percpu_counter_add(fbc, 1);
 141 }
 142
 143 static inline void percpu_counter_dec(struct percpu_counter *fbc)
 144 {
 145         percpu_counter_add(fbc, -1);
 146 }
 147
 148 static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
 149 {
 150         percpu_counter_add(fbc, -amount);
 151 }
 152
 153 #endif /* _LINUX_PERCPU_COUNTER_H */