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authorJohn W. Linville <linville@tuxdriver.com>2010-12-13 15:20:45 -0500
committerJohn W. Linville <linville@tuxdriver.com>2010-12-13 15:20:45 -0500
commit1d212aa96e1b63459486f729af9a3fa38768b801 (patch)
treee91e74db57a5bb7884b4681cdb788d405ec8f10f /lib
parent8c4877a4128e7931077b024a891a4b284d8756a3 (diff)
parentb7613370db5ba66ad81e41cd3a5417fde4d5e03c (diff)
downloadlinux-linaro-android-1d212aa96e1b63459486f729af9a3fa38768b801.tar.gz
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/average.c20
1 files changed, 12 insertions, 8 deletions
diff --git a/lib/average.c b/lib/average.c
index f1d1b4660c4..5576c284149 100644
--- a/lib/average.c
+++ b/lib/average.c
@@ -8,6 +8,7 @@
#include <linux/module.h>
#include <linux/average.h>
#include <linux/bug.h>
+#include <linux/log2.h>
/**
* DOC: Exponentially Weighted Moving Average (EWMA)
@@ -24,18 +25,21 @@
* 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).
+ * of averages can be ULONG_MAX/(factor*weight). For performance reasons
+ * factor has to be a power of 2.
* @weight: Exponential weight, or decay rate. This defines how fast the
- * influence of older values decreases. Has to be bigger than 1.
+ * influence of older values decreases. For performance reasons weight has
+ * to be a power of 2.
*
* 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);
+ WARN_ON(!is_power_of_2(weight) || !is_power_of_2(factor));
+
+ avg->weight = ilog2(weight);
+ avg->factor = ilog2(factor);
avg->internal = 0;
- avg->weight = weight;
- avg->factor = factor;
}
EXPORT_SYMBOL(ewma_init);
@@ -49,9 +53,9 @@ EXPORT_SYMBOL(ewma_init);
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);
+ (((avg->internal << avg->weight) - avg->internal) +
+ (val << avg->factor)) >> avg->weight :
+ (val << avg->factor);
return avg;
}
EXPORT_SYMBOL(ewma_add);