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>
diff --git a/include/linux/average.h b/include/linux/average.h
index 7706e40..c6028fd 100644
--- a/include/linux/average.h
+++ b/include/linux/average.h
@@ -1,8 +1,6 @@
#ifndef _LINUX_AVERAGE_H
#define _LINUX_AVERAGE_H
-#include <linux/kernel.h>
-
/* Exponentially weighted moving average (EWMA) */
/* For more documentation see lib/average.c */
@@ -26,7 +24,7 @@
*/
static inline unsigned long ewma_read(const struct ewma *avg)
{
- return DIV_ROUND_CLOSEST(avg->internal, avg->factor);
+ return avg->internal >> avg->factor;
}
#endif /* _LINUX_AVERAGE_H */