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편집 파일: average.h

/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_AVERAGE_H #define _LINUX_AVERAGE_H #include <linux/bug.h> #include <linux/compiler.h> #include <linux/log2.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 = READ_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); \ \ WRITE_ONCE(e->internal, internal ? \ (((internal << weight_rcp) - internal) + \ (val << precision)) >> weight_rcp : \ (val << precision)); \ } #endif /* _LINUX_AVERAGE_H */