Return-path: Received: from mail.net.t-labs.tu-berlin.de ([130.149.220.252]:43681 "EHLO mail.net.t-labs.tu-berlin.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751523AbbBECTX (ORCPT ); Wed, 4 Feb 2015 21:19:23 -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 09/10] mac80211: reduce calculation costs of EWMA Date: Thu, 5 Feb 2015 03:13:19 +0100 Message-Id: <1423102400-9693-10-git-send-email-thomas@net.t-labs.tu-berlin.de> (sfid-20150205_031928_438437_3861E809) In-Reply-To: <1423102400-9693-1-git-send-email-thomas@net.t-labs.tu-berlin.de> References: <1423102400-9693-1-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 2 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 d047610..16b6e36 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