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mac80211: reduce calculation costs of EWMA

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This patch reduces the calculation costs of the EWMA macro from
"2x multiplication and 1 addition" down to "1x multiplication and
2x additions". This slightly improves performance depending on the
CPU architecture.

Signed-off-by: Thomas Huehn <thomas@net.t-labs.tu-berlin.de>
Acked-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Thomas Huehn 2015-03-24 21:09:42 +01:00 • committed by Johannes Berg
parent 50e55a8ea7
commit ade6d4a2ec
1 changed files with 6 additions and 1 deletions
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7
net/mac80211/rc80211_minstrel.h
View file

@ -27,7 +27,12 @@
static inline int static inline int
minstrel_ewma(int old, int new, int weight) minstrel_ewma(int old, int new, int weight)
{ {
return (new * (EWMA_DIV - weight) + old * weight) / EWMA_DIV; int diff, incr;
diff = new - old;
incr = (EWMA_DIV - weight) * diff / EWMA_DIV;
return old + incr;
} }
struct minstrel_rate_stats { struct minstrel_rate_stats {