/* * 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);