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linux-next/include/linux/average.h

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lib: Add generic exponentially weighted moving average (EWMA) function 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>
2010-11-16 09:58:37 +08:00
#ifndef _LINUX_AVERAGE_H
#define _LINUX_AVERAGE_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)
{
lib: Improve EWMA efficiency by using bitshifts Using bitshifts instead of division and multiplication should improve performance. That requires weight and factor to be powers of two, but i think this is something we can live with. Thanks to Peter Zijlstra for the improved formula! Signed-off-by: Bruno Randolf <br1@einfach.org> -- v2: use log2.h functions Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-12-02 18:50:37 +08:00
return avg->internal >> avg->factor;
lib: Add generic exponentially weighted moving average (EWMA) function 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>
2010-11-16 09:58:37 +08:00
}
#endif /* _LINUX_AVERAGE_H */
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