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lib: Add generic exponentially weighted moving average (EWMA) function

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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@einfach.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Bruno Randolf 2010-11-16 10:58:37 +09:00 • committed by John W. Linville
parent 50a9432dae
commit c5485a7e75
4 changed files with 94 additions and 0 deletions
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32
include/linux/average.h Normal file
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#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 void ewma_init(struct ewma *avg, unsigned long factor,
unsigned long weight);
extern struct ewma *ewma_add(struct ewma *avg, unsigned long val);
/**
* ewma_read() - Get average value
* @avg: Average structure
*
* Returns the average value held in @avg.
*/
static inline unsigned long ewma_read(const struct ewma *avg)
{
return DIV_ROUND_CLOSEST(avg->internal, avg->factor);
}
#endif /* _LINUX_AVERAGE_H */