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71 lines
2.4 KiB
71 lines
2.4 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef _LINUX_AVERAGE_H |
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#define _LINUX_AVERAGE_H |
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#include <linux/bug.h> |
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#include <linux/compiler.h> |
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#include <linux/log2.h> |
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/* |
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* Exponentially weighted moving average (EWMA) |
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* |
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* This implements a fixed-precision EWMA algorithm, with both the |
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* precision and fall-off coefficient determined at compile-time |
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* and built into the generated helper funtions. |
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* |
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* The first argument to the macro is the name that will be used |
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* for the struct and helper functions. |
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* |
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* The second argument, the precision, expresses how many bits are |
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* used for the fractional part of the fixed-precision values. |
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* |
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* The third argument, the weight reciprocal, determines how the |
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* new values will be weighed vs. the old state, new values will |
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* get weight 1/weight_rcp and old values 1-1/weight_rcp. Note |
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* that this parameter must be a power of two for efficiency. |
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*/ |
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#define DECLARE_EWMA(name, _precision, _weight_rcp) \ |
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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(_precision)); \ |
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BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ |
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/* \ |
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* Even if you want to feed it just 0/1 you should have \ |
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* some bits for the non-fractional part... \ |
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*/ \ |
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BUILD_BUG_ON((_precision) > 30); \ |
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BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ |
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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(_precision)); \ |
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BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ |
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BUILD_BUG_ON((_precision) > 30); \ |
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BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ |
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return e->internal >> (_precision); \ |
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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 = READ_ONCE(e->internal); \ |
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unsigned long weight_rcp = ilog2(_weight_rcp); \ |
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unsigned long precision = _precision; \ |
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\ |
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BUILD_BUG_ON(!__builtin_constant_p(_precision)); \ |
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BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ |
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BUILD_BUG_ON((_precision) > 30); \ |
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BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ |
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\ |
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WRITE_ONCE(e->internal, internal ? \ |
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(((internal << weight_rcp) - internal) + \ |
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(val << precision)) >> weight_rcp : \ |
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(val << precision)); \ |
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} |
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#endif /* _LINUX_AVERAGE_H */
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