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Release 4.12 include/linux/average.h

Directory: include/linux
#ifndef _LINUX_AVERAGE_H

#define _LINUX_AVERAGE_H

/*
 * Exponentially weighted moving average (EWMA)
 *
 * This implements a fixed-precision EWMA algorithm, with both the
 * precision and fall-off coefficient determined at compile-time
 * and built into the generated helper funtions.
 *
 * The first argument to the macro is the name that will be used
 * for the struct and helper functions.
 *
 * The second argument, the precision, expresses how many bits are
 * used for the fractional part of the fixed-precision values.
 *
 * The third argument, the weight reciprocal, determines how the
 * new values will be weighed vs. the old state, new values will
 * get weight 1/weight_rcp and old values 1-1/weight_rcp. Note
 * that this parameter must be a power of two for efficiency.
 */


#define DECLARE_EWMA(name, _precision, _weight_rcp)			\
	struct ewma_##name {                                            \
                unsigned long internal;                                 \
        };                                                              \
        static inline void ewma_##name##_init(struct ewma_##name *e)    \
        {                                                               \
                BUILD_BUG_ON(!__builtin_constant_p(_precision));        \
                BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));       \
		/*                                                      \
                 * Even if you want to feed it just 0/1 you should have \
                 * some bits for the non-fractional part...             \
                 */							\
                BUILD_BUG_ON((_precision) > 30);                        \
                BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);               \
                e->internal = 0;                                        \
        }                                                               \
        static inline unsigned long                                     \
        ewma_##name##_read(struct ewma_##name *e)                       \
        {                                                               \
                BUILD_BUG_ON(!__builtin_constant_p(_precision));        \
                BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));       \
                BUILD_BUG_ON((_precision) > 30);                        \
                BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);               \
                return e->internal >> (_precision);                     \
        }                                                               \
        static inline void ewma_##name##_add(struct ewma_##name *e,     \
                                             unsigned long val)         \
        {                                                               \
                unsigned long internal = ACCESS_ONCE(e->internal);      \
                unsigned long weight_rcp = ilog2(_weight_rcp);          \
                unsigned long precision = _precision;                   \
                                                                        \
                BUILD_BUG_ON(!__builtin_constant_p(_precision));        \
                BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));       \
                BUILD_BUG_ON((_precision) > 30);                        \
                BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);               \
                                                                        \
                ACCESS_ONCE(e->internal) = internal ?                   \
                        (((internal << weight_rcp) - internal) +        \
                                (val << precision)) >> weight_rcp :     \
                        (val << precision);                             \
        }

#endif /* _LINUX_AVERAGE_H */

Overall Contributors

PersonTokensPropCommitsCommitProp
Johannes Berg1562.50%266.67%
Bruno Randolf937.50%133.33%
Total24100.00%3100.00%
Directory: include/linux
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