Return-path: Received: from mail.net.t-labs.tu-berlin.de ([130.149.220.252]:49174 "EHLO mail.net.t-labs.tu-berlin.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752935AbbBMO6G (ORCPT ); Fri, 13 Feb 2015 09:58:06 -0500 From: Thomas Huehn To: linux-wireless@vger.kernel.org Cc: johannes@sipsolutions.net, nbd@nbd.name, thomas@net.t-labs.tu-berlin.de Subject: [PATCH v2 09/10] mac80211: reduce calculation costs of EWMA Date: Fri, 13 Feb 2015 15:57:51 +0100 Message-Id: <1423839472-15625-10-git-send-email-thomas@net.t-labs.tu-berlin.de> (sfid-20150213_155819_088585_11A0B77D) In-Reply-To: <1423839472-15625-1-git-send-email-thomas@net.t-labs.tu-berlin.de> References: <1423839472-15625-1-git-send-email-thomas@net.t-labs.tu-berlin.de> Sender: linux-wireless-owner@vger.kernel.org List-ID: 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 --- net/mac80211/rc80211_minstrel.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/mac80211/rc80211_minstrel.h b/net/mac80211/rc80211_minstrel.h index 6693d8d..38158b0 100644 --- a/net/mac80211/rc80211_minstrel.h +++ b/net/mac80211/rc80211_minstrel.h @@ -27,7 +27,12 @@ static inline int 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 { -- 2.2.2