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2377799c08
Having the EWMA parameters stored in the runtime struct imposes memory requirements for the constant values that could just be inlined in the code. This particularly makes sense if there are a lot of such structs, for example in mac80211 in the station table where each station has a number of these in an array, and there can be many stations. Provide a macro DECLARE_EWMA() that declares the necessary struct and inline functions to access it with the parameters hard-coded; using this also means the user no longer needs to 'select AVERAGE' as it's entirely self-contained. In the mac80211 case, on x86-64, this actually slightly *reduces* code size, while also saving 80 bytes of runtime memory per sta. Signed-off-by: Johannes Berg <johannes.berg@intel.com>
70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
#ifndef _LINUX_AVERAGE_H
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#define _LINUX_AVERAGE_H
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/* Exponentially weighted moving average (EWMA) */
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/* For more documentation see lib/average.c */
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struct ewma {
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unsigned long internal;
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unsigned long factor;
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unsigned long weight;
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};
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extern void ewma_init(struct ewma *avg, unsigned long factor,
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unsigned long weight);
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extern struct ewma *ewma_add(struct ewma *avg, unsigned long val);
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/**
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* ewma_read() - Get average value
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* @avg: Average structure
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*
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* Returns the average value held in @avg.
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*/
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static inline unsigned long ewma_read(const struct ewma *avg)
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{
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return avg->internal >> avg->factor;
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}
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#define DECLARE_EWMA(name, _factor, _weight) \
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struct ewma_##name { \
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unsigned long internal; \
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}; \
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static inline void ewma_##name##_init(struct ewma_##name *e) \
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{ \
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BUILD_BUG_ON(!__builtin_constant_p(_factor)); \
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BUILD_BUG_ON(!__builtin_constant_p(_weight)); \
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BUILD_BUG_ON_NOT_POWER_OF_2(_factor); \
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BUILD_BUG_ON_NOT_POWER_OF_2(_weight); \
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e->internal = 0; \
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} \
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static inline unsigned long \
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ewma_##name##_read(struct ewma_##name *e) \
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{ \
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BUILD_BUG_ON(!__builtin_constant_p(_factor)); \
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BUILD_BUG_ON(!__builtin_constant_p(_weight)); \
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BUILD_BUG_ON_NOT_POWER_OF_2(_factor); \
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BUILD_BUG_ON_NOT_POWER_OF_2(_weight); \
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return e->internal >> ilog2(_factor); \
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} \
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static inline void ewma_##name##_add(struct ewma_##name *e, \
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unsigned long val) \
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{ \
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unsigned long internal = ACCESS_ONCE(e->internal); \
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unsigned long weight = ilog2(_weight); \
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unsigned long factor = ilog2(_factor); \
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\
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BUILD_BUG_ON(!__builtin_constant_p(_factor)); \
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BUILD_BUG_ON(!__builtin_constant_p(_weight)); \
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BUILD_BUG_ON_NOT_POWER_OF_2(_factor); \
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BUILD_BUG_ON_NOT_POWER_OF_2(_weight); \
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\
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ACCESS_ONCE(e->internal) = internal ? \
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(((internal << weight) - internal) + \
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(val << factor)) >> weight : \
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(val << factor); \
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}
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#endif /* _LINUX_AVERAGE_H */
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