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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)
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 f1d1b4660c42..5576c2841496 100644
--- a/lib/average.c
+++ b/lib/average.c
@@ -8,6 +8,7 @@
8#include <linux/module.h> 8#include <linux/module.h>
9#include <linux/average.h> 9#include <linux/average.h>
10#include <linux/bug.h> 10#include <linux/bug.h>
11#include <linux/log2.h>
11 12
12/** 13/**
13 * DOC: Exponentially Weighted Moving Average (EWMA) 14 * DOC: Exponentially Weighted Moving Average (EWMA)
@@ -24,18 +25,21 @@
24 * ewma_init() - Initialize EWMA parameters 25 * ewma_init() - Initialize EWMA parameters
25 * @avg: Average structure 26 * @avg: Average structure
26 * @factor: Factor to use for the scaled up internal value. The maximum value 27 * @factor: Factor to use for the scaled up internal value. The maximum value
27 * of averages can be ULONG_MAX/(factor*weight). 28 * of averages can be ULONG_MAX/(factor*weight). For performance reasons
29 * factor has to be a power of 2.
28 * @weight: Exponential weight, or decay rate. This defines how fast the 30 * @weight: Exponential weight, or decay rate. This defines how fast the
29 * influence of older values decreases. Has to be bigger than 1. 31 * influence of older values decreases. For performance reasons weight has
32 * to be a power of 2.
30 * 33 *
31 * Initialize the EWMA parameters for a given struct ewma @avg. 34 * Initialize the EWMA parameters for a given struct ewma @avg.
32 */ 35 */
33void ewma_init(struct ewma *avg, unsigned long factor, unsigned long weight) 36void ewma_init(struct ewma *avg, unsigned long factor, unsigned long weight)
34{ 37{
35 WARN_ON(weight <= 1 || factor == 0); 38 WARN_ON(!is_power_of_2(weight) || !is_power_of_2(factor));
39
40 avg->weight = ilog2(weight);
41 avg->factor = ilog2(factor);
36 avg->internal = 0; 42 avg->internal = 0;
37 avg->weight = weight;
38 avg->factor = factor;
39} 43}
40EXPORT_SYMBOL(ewma_init); 44EXPORT_SYMBOL(ewma_init);
41 45
@@ -49,9 +53,9 @@ EXPORT_SYMBOL(ewma_init);
49struct ewma *ewma_add(struct ewma *avg, unsigned long val) 53struct ewma *ewma_add(struct ewma *avg, unsigned long val)
50{ 54{
51 avg->internal = avg->internal ? 55 avg->internal = avg->internal ?
52 (((avg->internal * (avg->weight - 1)) + 56 (((avg->internal << avg->weight) - avg->internal) +
53 (val * avg->factor)) / avg->weight) : 57 (val << avg->factor)) >> avg->weight :
54 (val * avg->factor); 58 (val << avg->factor);
55 return avg; 59 return avg;
56} 60}
57EXPORT_SYMBOL(ewma_add); 61EXPORT_SYMBOL(ewma_add);