mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-24 13:13:57 +08:00
eb1e011a14
Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
67 lines
2.3 KiB
C
67 lines
2.3 KiB
C
#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 */
|