The patch titled
lib: add generic exponentially weighted moving average (EWMA) function
has been removed from the -mm tree. Its filename was
lib-add-generic-exponentially-weighted-moving-average-ewma-function.patch
This patch was dropped because it is obsolete
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: lib: add generic exponentially weighted moving average (EWMA) function
From: Bruno Randolf <br1@xxxxxxxxxxx>
This adds generic functions for calculating Exponentially Weighted Moving
Averages (EWMA). This implementation makes use of a structure which keeps
the EWMA parameters and a scaled up internal representation to reduce
rounding errors.
The original idea for this implementation came from the rt2x00 driver
(rt2x00link.c). I would like to use it in several places in the mac80211
and ath5k code and I hope it can be useful in many other places in the
kernel code.
Signed-off-by: Bruno Randolf <br1@xxxxxxxxxxx>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Randy Dunlap <randy.dunlap@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: "John W. Linville" <linville@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/average.h | 32 ++++++++++++++++++++
lib/Makefile | 2 -
lib/average.c | 58 ++++++++++++++++++++++++++++++++++++++
3 files changed, 91 insertions(+), 1 deletion(-)
diff -puN /dev/null include/linux/average.h
--- /dev/null
+++ a/include/linux/average.h
@@ -0,0 +1,32 @@
+#ifndef _LINUX_AVERAGE_H
+#define _LINUX_AVERAGE_H
+
+#include <linux/kernel.h>
+
+/* Exponentially weighted moving average (EWMA) */
+
+/* For more documentation see lib/average.c */
+
+struct ewma {
+ unsigned long internal;
+ unsigned long factor;
+ unsigned long weight;
+};
+
+extern struct ewma *ewma_init(struct ewma *avg, unsigned long factor,
+ unsigned long weight);
+
+extern struct ewma *ewma_add(struct ewma *avg, unsigned long val);
+
+/**
+ * ewma_get() - Get average value
+ * @avg: Average structure
+ *
+ * Returns the average value held in @avg.
+ */
+static inline unsigned long ewma_get(const struct ewma *avg)
+{
+ return DIV_ROUND_CLOSEST(avg->internal, avg->factor);
+}
+
+#endif /* _LINUX_AVERAGE_H */
diff -puN lib/Makefile~lib-add-generic-exponentially-weighted-moving-average-ewma-function lib/Makefile
--- a/lib/Makefile~lib-add-generic-exponentially-weighted-moving-average-ewma-function
+++ a/lib/Makefile
@@ -21,7 +21,7 @@ lib-y += kobject.o kref.o klist.o
obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
- string_helpers.o gcd.o lcm.o list_sort.o uuid.o
+ string_helpers.o gcd.o lcm.o list_sort.o uuid.o average.o
ifeq ($(CONFIG_DEBUG_KOBJECT),y)
CFLAGS_kobject.o += -DDEBUG
diff -puN /dev/null lib/average.c
--- /dev/null
+++ a/lib/average.c
@@ -0,0 +1,58 @@
+/*
+ * 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>
+
+/**
+ * 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.
+ */
+struct ewma *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;
+ return avg;
+}
+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);
_
Patches currently in -mm which might be from br1@xxxxxxxxxxx are
linux-next.patch
lib-add-generic-exponentially-weighted-moving-average-ewma-function-fix.patch
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