Since commit eb1e011a1474 ("average: change to declare precision,
not factor") the definition of DECLARE_EWMA has changed so we
need a backport for the new macro as it differs. Changing the
strategy by checking the kernel version and #undef the macro to
be sure we do not run into macro redefinition issue.
Signed-off-by: Arend van Spriel <arend.vanspriel@xxxxxxxxxxxx>
---
backport/backport-include/linux/average.h | 65 +++++++++++++++++++++----------
1 file changed, 44 insertions(+), 21 deletions(-)
diff --git a/backport/backport-include/linux/average.h b/backport/backport-include/linux/average.h
index 5d80041..51702fb 100644
--- a/backport/backport-include/linux/average.h
+++ b/backport/backport-include/linux/average.h
@@ -2,45 +2,68 @@
#define __BACKPORT_AVERAGE
#include_next <linux/average.h>
-#ifndef DECLARE_EWMA
-#define DECLARE_EWMA(name, _factor, _weight) \
+/*
+ * 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.
+ */
+#if LINUX_VERSION_IS_LESS(4, 11, 0)
+#undef DECLARE_EWMA
+#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(_factor)); \
- BUILD_BUG_ON(!__builtin_constant_p(_weight)); \
- BUILD_BUG_ON_NOT_POWER_OF_2(_factor); \
- BUILD_BUG_ON_NOT_POWER_OF_2(_weight); \
+ 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(_factor)); \
- BUILD_BUG_ON(!__builtin_constant_p(_weight)); \
- BUILD_BUG_ON_NOT_POWER_OF_2(_factor); \
- BUILD_BUG_ON_NOT_POWER_OF_2(_weight); \
- return e->internal >> ilog2(_factor); \
+ 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 = ilog2(_weight); \
- unsigned long factor = ilog2(_factor); \
+ unsigned long weight_rcp = ilog2(_weight_rcp); \
+ unsigned long precision = _precision; \
\
- BUILD_BUG_ON(!__builtin_constant_p(_factor)); \
- BUILD_BUG_ON(!__builtin_constant_p(_weight)); \
- BUILD_BUG_ON_NOT_POWER_OF_2(_factor); \
- BUILD_BUG_ON_NOT_POWER_OF_2(_weight); \
+ 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) - internal) + \
- (val << factor)) >> weight : \
- (val << factor); \
+ (((internal << weight_rcp) - internal) + \
+ (val << precision)) >> weight_rcp : \
+ (val << precision); \
}
-#endif /* DECLARE_EWMA */
+#endif /* LINUX_VERSION_IS_LESS(4, 11, 0) */
#endif /* __BACKPORT_AVERAGE */
--
1.9.1
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