include/linux/average.h

   1 #ifndef _LINUX_AVERAGE_H
   2 #define _LINUX_AVERAGE_H
   3
   4 /* Exponentially weighted moving average (EWMA) */
   5
   6 #define DECLARE_EWMA(name, _factor, _weight)                            \
   7         struct ewma_##name {                                            \
   8                 unsigned long internal;                                 \
   9         };                                                              \
  10         static inline void ewma_##name##_init(struct ewma_##name *e)    \
  11         {                                                               \
  12                 BUILD_BUG_ON(!__builtin_constant_p(_factor));           \
  13                 BUILD_BUG_ON(!__builtin_constant_p(_weight));           \
  14                 BUILD_BUG_ON_NOT_POWER_OF_2(_factor);                   \
  15                 BUILD_BUG_ON_NOT_POWER_OF_2(_weight);                   \
  16                 e->internal = 0;                                        \
  17         }                                                               \
  18         static inline unsigned long                                     \
  19         ewma_##name##_read(struct ewma_##name *e)                       \
  20         {                                                               \
  21                 BUILD_BUG_ON(!__builtin_constant_p(_factor));           \
  22                 BUILD_BUG_ON(!__builtin_constant_p(_weight));           \
  23                 BUILD_BUG_ON_NOT_POWER_OF_2(_factor);                   \
  24                 BUILD_BUG_ON_NOT_POWER_OF_2(_weight);                   \
  25                 return e->internal >> ilog2(_factor);                   \
  26         }                                                               \
  27         static inline void ewma_##name##_add(struct ewma_##name *e,     \
  28                                              unsigned long val)         \
  29         {                                                               \
  30                 unsigned long internal = ACCESS_ONCE(e->internal);      \
  31                 unsigned long weight = ilog2(_weight);                  \
  32                 unsigned long factor = ilog2(_factor);                  \
  33                                                                         \
  34                 BUILD_BUG_ON(!__builtin_constant_p(_factor));           \
  35                 BUILD_BUG_ON(!__builtin_constant_p(_weight));           \
  36                 BUILD_BUG_ON_NOT_POWER_OF_2(_factor);                   \
  37                 BUILD_BUG_ON_NOT_POWER_OF_2(_weight);                   \
  38                                                                         \
  39                 ACCESS_ONCE(e->internal) = internal ?                   \
  40                         (((internal << weight) - internal) +            \
  41                                 (val << factor)) >> weight :            \
  42                         (val << factor);                                \
  43         }
  44
  45 #endif /* _LINUX_AVERAGE_H */