diff options
author | Stephen Rothwell <sfr@canb.auug.org.au> | 2010-12-10 11:13:40 +1100 |
---|---|---|
committer | Stephen Rothwell <sfr@canb.auug.org.au> | 2010-12-10 11:13:40 +1100 |
commit | 3054167cf9b547cf20c14465cb50f411425042b3 (patch) | |
tree | dec3f5f512890e3663e8d8b1bdebe1510191c47b /lib | |
parent | fc1a45d55c50363a39a42f7d0209ffa4f10e468d (diff) | |
parent | b7613370db5ba66ad81e41cd3a5417fde4d5e03c (diff) |
Merge remote branch 'wireless/master'
Diffstat (limited to 'lib')
-rw-r--r-- | lib/Kconfig | 3 | ||||
-rw-r--r-- | lib/Makefile | 2 | ||||
-rw-r--r-- | lib/average.c | 61 |
3 files changed, 66 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..5576c2841496 --- /dev/null +++ b/lib/average.c @@ -0,0 +1,61 @@ +/* + * 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> +#include <linux/log2.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). 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. 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(!is_power_of_2(weight) || !is_power_of_2(factor)); + + avg->weight = ilog2(weight); + avg->factor = ilog2(factor); + avg->internal = 0; +} +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) - avg->internal) + + (val << avg->factor)) >> avg->weight : + (val << avg->factor); + return avg; +} +EXPORT_SYMBOL(ewma_add); |