batman-adv/patches/0001-batman-adv-average-change-to-declare-precision-not-f.patch

   1 From: Johannes Berg <johannes.berg@intel.com>
   2 Date: Wed, 15 Feb 2017 09:49:26 +0100
   3 Subject: [PATCH] batman-adv: average: change to declare precision, not factor
   4
   5 Declaring the factor is counter-intuitive, and people are prone
   6 to using small(-ish) values even when that makes no sense.
   7
   8 Change the DECLARE_EWMA() macro to take the fractional precision,
   9 in bits, rather than a factor, and update all users.
  10
  11 While at it, add some more documentation.
  12
  13 Acked-by: David S. Miller <davem@davemloft.net>
  14 Signed-off-by: Johannes Berg <johannes.berg@intel.com>
  15 [sven@narfation.org: Added compatibility code]
  16 Signed-off-by: Sven Eckelmann <sven@narfation.org>
  17 ---
  18  compat-include/linux/average.h | 67 +++++++++++++++++++++++++++---------------
  19  net/batman-adv/types.h         |  2 +-
  20  2 files changed, 45 insertions(+), 24 deletions(-)
  21
  22 diff --git a/compat-include/linux/average.h b/compat-include/linux/average.h
  23 index ec022cb6..a1e3c254 100644
  24 --- a/compat-include/linux/average.h
  25 +++ b/compat-include/linux/average.h
  26 @@ -26,49 +26,70 @@
  27
  28  #include <linux/bug.h>
  29
  30 -#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 3, 0)
  31 +#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 3, 0)
  32 +#undef DECLARE_EWMA
  33 +#endif /* < KERNEL_VERSION(4, 3, 0) */
  34
  35 -/* Exponentially weighted moving average (EWMA) */
  36 +/*
  37 + * Exponentially weighted moving average (EWMA)
  38 + *
  39 + * This implements a fixed-precision EWMA algorithm, with both the
  40 + * precision and fall-off coefficient determined at compile-time
  41 + * and built into the generated helper funtions.
  42 + *
  43 + * The first argument to the macro is the name that will be used
  44 + * for the struct and helper functions.
  45 + *
  46 + * The second argument, the precision, expresses how many bits are
  47 + * used for the fractional part of the fixed-precision values.
  48 + *
  49 + * The third argument, the weight reciprocal, determines how the
  50 + * new values will be weighed vs. the old state, new values will
  51 + * get weight 1/weight_rcp and old values 1-1/weight_rcp. Note
  52 + * that this parameter must be a power of two for efficiency.
  53 + */
  54
  55 -#define DECLARE_EWMA(name, _factor, _weight)                           \
  56 +#define DECLARE_EWMA(name, _precision, _weight_rcp)                    \
  57         struct ewma_##name {                                            \
  58                 unsigned long internal;                                 \
  59         };                                                              \
  60         static inline void ewma_##name##_init(struct ewma_##name *e)    \
  61         {                                                               \
  62 -               BUILD_BUG_ON(!__builtin_constant_p(_factor));           \
  63 -               BUILD_BUG_ON(!__builtin_constant_p(_weight));           \
  64 -               BUILD_BUG_ON_NOT_POWER_OF_2(_factor);                   \
  65 -               BUILD_BUG_ON_NOT_POWER_OF_2(_weight);                   \
  66 +               BUILD_BUG_ON(!__builtin_constant_p(_precision));        \
  67 +               BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));       \
  68 +               /*                                                      \
  69 +                * Even if you want to feed it just 0/1 you should have \
  70 +                * some bits for the non-fractional part...             \
  71 +                */                                                     \
  72 +               BUILD_BUG_ON((_precision) > 30);                        \
  73 +               BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);               \
  74                 e->internal = 0;                                        \
  75         }                                                               \
  76         static inline unsigned long                                     \
  77         ewma_##name##_read(struct ewma_##name *e)                       \
  78         {                                                               \
  79 -               BUILD_BUG_ON(!__builtin_constant_p(_factor));           \
  80 -               BUILD_BUG_ON(!__builtin_constant_p(_weight));           \
  81 -               BUILD_BUG_ON_NOT_POWER_OF_2(_factor);                   \
  82 -               BUILD_BUG_ON_NOT_POWER_OF_2(_weight);                   \
  83 -               return e->internal >> ilog2(_factor);                   \
  84 +               BUILD_BUG_ON(!__builtin_constant_p(_precision));        \
  85 +               BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));       \
  86 +               BUILD_BUG_ON((_precision) > 30);                        \
  87 +               BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);               \
  88 +               return e->internal >> (_precision);                     \
  89         }                                                               \
  90         static inline void ewma_##name##_add(struct ewma_##name *e,     \
  91                                              unsigned long val)         \
  92         {                                                               \
  93                 unsigned long internal = ACCESS_ONCE(e->internal);      \
  94 -               unsigned long weight = ilog2(_weight);                  \
  95 -               unsigned long factor = ilog2(_factor);                  \
  96 +               unsigned long weight_rcp = ilog2(_weight_rcp);          \
  97 +               unsigned long precision = _precision;                   \
  98                                                                         \
  99 -               BUILD_BUG_ON(!__builtin_constant_p(_factor));           \
 100 -               BUILD_BUG_ON(!__builtin_constant_p(_weight));           \
 101 -               BUILD_BUG_ON_NOT_POWER_OF_2(_factor);                   \
 102 -               BUILD_BUG_ON_NOT_POWER_OF_2(_weight);                   \
 103 +               BUILD_BUG_ON(!__builtin_constant_p(_precision));        \
 104 +               BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));       \
 105 +               BUILD_BUG_ON((_precision) > 30);                        \
 106 +               BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);               \
 107                                                                         \
 108                 ACCESS_ONCE(e->internal) = internal ?                   \
 109 -                       (((internal << weight) - internal) +            \
 110 -                               (val << factor)) >> weight :            \
 111 -                       (val << factor);                                \
 112 +                       (((internal << weight_rcp) - internal) +        \
 113 +                               (val << precision)) >> weight_rcp :     \
 114 +                       (val << precision);                             \
 115         }
 116
 117 -#endif /* < KERNEL_VERSION(4, 3, 0) */
 118 -
 119  #endif /* _NET_BATMAN_ADV_COMPAT_LINUX_AVERAGE_H */
 120 diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
 121 index 8f64a5c0..66b25e41 100644
 122 --- a/net/batman-adv/types.h
 123 +++ b/net/batman-adv/types.h
 124 @@ -402,7 +402,7 @@ struct batadv_gw_node {
 125         struct rcu_head rcu;
 126  };
 127
 128 -DECLARE_EWMA(throughput, 1024, 8)
 129 +DECLARE_EWMA(throughput, 10, 8)
 130
 131  /**
 132   * struct batadv_hardif_neigh_node_bat_v - B.A.T.M.A.N. V private neighbor