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authorJohn W. Linville <linville@tuxdriver.com>2010-11-24 16:49:20 -0500
committerJohn W. Linville <linville@tuxdriver.com>2010-11-24 16:49:20 -0500
commit51cce8a590c4696d62bfacc63378d1036084cef7 (patch)
treedc24485bdff37ca6a83c69e93ffdbe5c5807b59d /lib
parent2fe66ec242d3f76e3b0101f36419e7e5405bcff3 (diff)
parent4f8559383c41262b50dc758e2e310f257ce6a14d (diff)
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next-2.6 into for-davem
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig3
-rw-r--r--lib/Makefile2
-rw-r--r--lib/average.c57
3 files changed, 62 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index fa9bf2c06199..3116aa631af6 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -210,4 +210,7 @@ config GENERIC_ATOMIC64
config LRU_CACHE
tristate
+config AVERAGE
+ bool
+
endmenu
diff --git a/lib/Makefile b/lib/Makefile
index e6a3763b8212..76d3b8514903 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -106,6 +106,8 @@ obj-$(CONFIG_GENERIC_ATOMIC64) += atomic64.o
obj-$(CONFIG_ATOMIC64_SELFTEST) += atomic64_test.o
+obj-$(CONFIG_AVERAGE) += average.o
+
hostprogs-y := gen_crc32table
clean-files := crc32table.h
diff --git a/lib/average.c b/lib/average.c
new file mode 100644
index 000000000000..f1d1b4660c42
--- /dev/null
+++ b/lib/average.c
@@ -0,0 +1,57 @@
+/*
+ * lib/average.c
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/average.h>
+#include <linux/bug.h>
+
+/**
+ * DOC: Exponentially Weighted Moving Average (EWMA)
+ *
+ * These are generic functions for calculating Exponentially Weighted Moving
+ * Averages (EWMA). We keep a structure with the EWMA parameters and a scaled
+ * up internal representation of the average value to prevent rounding errors.
+ * The factor for scaling up and the exponential weight (or decay rate) have to
+ * be specified thru the init fuction. The structure should not be accessed
+ * directly but only thru the helper functions.
+ */
+
+/**
+ * ewma_init() - Initialize EWMA parameters
+ * @avg: Average structure
+ * @factor: Factor to use for the scaled up internal value. The maximum value
+ * of averages can be ULONG_MAX/(factor*weight).
+ * @weight: Exponential weight, or decay rate. This defines how fast the
+ * influence of older values decreases. Has to be bigger than 1.
+ *
+ * Initialize the EWMA parameters for a given struct ewma @avg.
+ */
+void ewma_init(struct ewma *avg, unsigned long factor, unsigned long weight)
+{
+ WARN_ON(weight <= 1 || factor == 0);
+ avg->internal = 0;
+ avg->weight = weight;
+ avg->factor = factor;
+}
+EXPORT_SYMBOL(ewma_init);
+
+/**
+ * ewma_add() - Exponentially weighted moving average (EWMA)
+ * @avg: Average structure
+ * @val: Current value
+ *
+ * Add a sample to the average.
+ */
+struct ewma *ewma_add(struct ewma *avg, unsigned long val)
+{
+ avg->internal = avg->internal ?
+ (((avg->internal * (avg->weight - 1)) +
+ (val * avg->factor)) / avg->weight) :
+ (val * avg->factor);
+ return avg;
+}
+EXPORT_SYMBOL(ewma_add);

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