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>

1 files changed, 1 insertions, 3 deletions

diff --git a/include/linux/average.h b/include/linux/average.h
index 7706e40f95fa..c6028fd742c1 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 @@ extern struct ewma *ewma_add(struct ewma *avg, unsigned long val);
  */
 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 */