133 lines
4.9 KiB
Diff
133 lines
4.9 KiB
Diff
From: Johannes Berg <johannes.berg@intel.com>
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Date: Wed, 15 Feb 2017 09:49:26 +0100
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Subject: [PATCH] batman-adv: average: change to declare precision, not factor
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Declaring the factor is counter-intuitive, and people are prone
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to using small(-ish) values even when that makes no sense.
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Change the DECLARE_EWMA() macro to take the fractional precision,
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in bits, rather than a factor, and update all users.
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While at it, add some more documentation.
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Acked-by: David S. Miller <davem@davemloft.net>
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Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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[sven@narfation.org: Added compatibility code]
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Signed-off-by: Sven Eckelmann <sven@narfation.org>
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---
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compat-include/linux/average.h | 67 +++++++++++++++++++++++++++---------------
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net/batman-adv/types.h | 2 +-
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2 files changed, 45 insertions(+), 24 deletions(-)
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diff --git a/compat-include/linux/average.h b/compat-include/linux/average.h
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index ec022cb6..a1e3c254 100644
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--- a/compat-include/linux/average.h
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+++ b/compat-include/linux/average.h
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@@ -26,49 +26,70 @@
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#include <linux/bug.h>
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-#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0)
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+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
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+#undef DECLARE_EWMA
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+#endif /* < KERNEL_VERSION(4, 3, 0) */
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-/* Exponentially weighted moving average (EWMA) */
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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, _factor, _weight) \
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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(_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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+ 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(_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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+ 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 = 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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+ 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(_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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+ 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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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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+ (((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 /* < KERNEL_VERSION(4, 3, 0) */
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-
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#endif /* _NET_BATMAN_ADV_COMPAT_LINUX_AVERAGE_H */
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diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
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index 8f64a5c0..66b25e41 100644
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--- a/net/batman-adv/types.h
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+++ b/net/batman-adv/types.h
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@@ -402,7 +402,7 @@ struct batadv_gw_node {
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struct rcu_head rcu;
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};
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-DECLARE_EWMA(throughput, 1024, 8)
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+DECLARE_EWMA(throughput, 10, 8)
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/**
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* struct batadv_hardif_neigh_node_bat_v - B.A.T.M.A.N. V private neighbor
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