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authorJohannes Berg <johannes.berg@intel.com>2017-02-15 09:49:26 +0100
committerJohannes Berg <johannes.berg@intel.com>2017-03-02 08:32:46 +0100
commiteb1e011a14748a1d9df9a7d7df9a5711721a1bdb (patch)
tree599710c96a23bcbc25423cb0a99696dd0b257c7b
parent48cac18ecf1de82f76259a54402c3adb7839ad01 (diff)
average: change to declare precision, not factor
Declaring the factor is counter-intuitive, and people are prone to using small(-ish) values even when that makes no sense. Change the DECLARE_EWMA() macro to take the fractional precision, in bits, rather than a factor, and update all users. While at it, add some more documentation. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
-rw-r--r--drivers/net/virtio_net.c2
-rw-r--r--drivers/net/wireless/ath/ath5k/ath5k.h2
-rw-r--r--drivers/net/wireless/ralink/rt2x00/rt2x00.h2
-rw-r--r--include/linux/average.h61
-rw-r--r--net/batman-adv/types.h2
-rw-r--r--net/mac80211/ieee80211_i.h2
-rw-r--r--net/mac80211/sta_info.h2
7 files changed, 47 insertions, 26 deletions
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index bf95016..e9d7e2b 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -51,7 +51,7 @@ module_param(gso, bool, 0444);
* at once, the weight is chosen so that the EWMA will be insensitive to short-
* term, transient changes in packet size.
*/
-DECLARE_EWMA(pkt_len, 1, 64)
+DECLARE_EWMA(pkt_len, 0, 64)
/* With mergeable buffers we align buffer address and use the low bits to
* encode its true size. Buffer size is up to 1 page so we need to align to
diff --git a/drivers/net/wireless/ath/ath5k/ath5k.h b/drivers/net/wireless/ath/ath5k/ath5k.h
index 67fedb6..979800c 100644
--- a/drivers/net/wireless/ath/ath5k/ath5k.h
+++ b/drivers/net/wireless/ath/ath5k/ath5k.h
@@ -1252,7 +1252,7 @@ struct ath5k_statistics {
#define ATH5K_TXQ_LEN_MAX (ATH_TXBUF / 4) /* bufs per queue */
#define ATH5K_TXQ_LEN_LOW (ATH5K_TXQ_LEN_MAX / 2) /* low mark */
-DECLARE_EWMA(beacon_rssi, 1024, 8)
+DECLARE_EWMA(beacon_rssi, 10, 8)
/* Driver state associated with an instance of a device */
struct ath5k_hw {
diff --git a/drivers/net/wireless/ralink/rt2x00/rt2x00.h b/drivers/net/wireless/ralink/rt2x00/rt2x00.h
index 26869b3..3407878 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/ralink/rt2x00/rt2x00.h
@@ -257,7 +257,7 @@ struct link_qual {
int tx_failed;
};
-DECLARE_EWMA(rssi, 1024, 8)
+DECLARE_EWMA(rssi, 10, 8)
/*
* Antenna settings about the currently active link.
diff --git a/include/linux/average.h b/include/linux/average.h
index d04aa58..7ddaf34 100644
--- a/include/linux/average.h
+++ b/include/linux/average.h
@@ -1,45 +1,66 @@
#ifndef _LINUX_AVERAGE_H
#define _LINUX_AVERAGE_H
-/* Exponentially weighted moving average (EWMA) */
+/*
+ * 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.
+ */
-#define DECLARE_EWMA(name, _factor, _weight) \
+#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 /* _LINUX_AVERAGE_H */
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 8f64a5c..66b25e4 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -402,7 +402,7 @@ struct batadv_gw_node {
struct rcu_head rcu;
};
-DECLARE_EWMA(throughput, 1024, 8)
+DECLARE_EWMA(throughput, 10, 8)
/**
* struct batadv_hardif_neigh_node_bat_v - B.A.T.M.A.N. V private neighbor
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 159a1a7..0e71843 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -428,7 +428,7 @@ struct ieee80211_sta_tx_tspec {
bool downgraded;
};
-DECLARE_EWMA(beacon_signal, 16, 4)
+DECLARE_EWMA(beacon_signal, 4, 4)
struct ieee80211_if_managed {
struct timer_list timer;
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 15599c7..e65cda3 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -372,7 +372,7 @@ struct mesh_sta {
unsigned int fail_avg;
};
-DECLARE_EWMA(signal, 1024, 8)
+DECLARE_EWMA(signal, 10, 8)
struct ieee80211_sta_rx_stats {
unsigned long packets;