linux-stable/include/linux/average.h
Bruno Randolf af55688435 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>
2010-12-06 15:58:43 -05:00

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C

#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)
{
return avg->internal >> avg->factor;
}
#endif /* _LINUX_AVERAGE_H */