[mirror_ubuntu-artful-kernel.git] / include / linux / average.h

#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 */
Commit	Line	Data
c5485a7e BR	1	#ifndef _LINUX_AVERAGE_H
	2	#define _LINUX_AVERAGE_H
	3
eb1e011a JB	4	/*
	5	* Exponentially weighted moving average (EWMA)
	6	*
	7	* This implements a fixed-precision EWMA algorithm, with both the
	8	* precision and fall-off coefficient determined at compile-time
	9	* and built into the generated helper funtions.
	10	*
	11	* The first argument to the macro is the name that will be used
	12	* for the struct and helper functions.
	13	*
	14	* The second argument, the precision, expresses how many bits are
	15	* used for the fractional part of the fixed-precision values.
	16	*
	17	* The third argument, the weight reciprocal, determines how the
	18	* new values will be weighed vs. the old state, new values will
	19	* get weight 1/weight_rcp and old values 1-1/weight_rcp. Note
	20	* that this parameter must be a power of two for efficiency.
	21	*/
c5485a7e	22
eb1e011a	23	#define DECLARE_EWMA(name, _precision, _weight_rcp) \
2377799c JB	24	struct ewma_##name { \
	25	unsigned long internal; \
	26	}; \
	27	static inline void ewma_##name##_init(struct ewma_##name *e) \
	28	{ \
eb1e011a JB	29	BUILD_BUG_ON(!__builtin_constant_p(_precision)); \
	30	BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \
	31	/* \
	32	* Even if you want to feed it just 0/1 you should have \
	33	* some bits for the non-fractional part... \
	34	*/ \
	35	BUILD_BUG_ON((_precision) > 30); \
	36	BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \
2377799c JB	37	e->internal = 0; \
	38	} \
	39	static inline unsigned long \
	40	ewma_##name##_read(struct ewma_##name *e) \
	41	{ \
eb1e011a JB	42	BUILD_BUG_ON(!__builtin_constant_p(_precision)); \
	43	BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \
	44	BUILD_BUG_ON((_precision) > 30); \
	45	BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \
	46	return e->internal >> (_precision); \
2377799c JB	47	} \
	48	static inline void ewma_##name##_add(struct ewma_##name *e, \
	49	unsigned long val) \
	50	{ \
	51	unsigned long internal = ACCESS_ONCE(e->internal); \
eb1e011a JB	52	unsigned long weight_rcp = ilog2(_weight_rcp); \
eb1e011a JB	53	unsigned long precision = _precision; \
2377799c	54	\
eb1e011a JB	55	BUILD_BUG_ON(!__builtin_constant_p(_precision)); \
	56	BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \
	57	BUILD_BUG_ON((_precision) > 30); \
	58	BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \
2377799c JB	59	\
2377799c JB	60	ACCESS_ONCE(e->internal) = internal ? \
eb1e011a JB	61	(((internal << weight_rcp) - internal) + \
	62	(val << precision)) >> weight_rcp : \
	63	(val << precision); \
2377799c JB	64	}
2377799c JB	65
c5485a7e	66	#endif /* _LINUX_AVERAGE_H */