From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55CFFC43381 for ; Fri, 15 Jan 2021 12:04:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2068222583 for ; Fri, 15 Jan 2021 12:04:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730706AbhAOMEP (ORCPT ); Fri, 15 Jan 2021 07:04:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726085AbhAOMEP (ORCPT ); Fri, 15 Jan 2021 07:04:15 -0500 Received: from nbd.name (nbd.name [IPv6:2a01:4f8:221:3d45::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C5CF4C06179C for ; Fri, 15 Jan 2021 04:02:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=nbd.name; s=20160729; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=OVQpEEDveWeQgJiIBCw9TIVF7ODOND/QMES/7ziT390=; b=IbqAymDswBEYitg+EClnkQUyZM 9a6Bgzzi9qfNRdX+BdtAVMmDsffO+k1JaEgRBddaz7eNSRJHhHvPZCrPTudwyO0aDhbkojOcFhjjC hQzqer8ALxmA95OPA+yQWEyGPfUdkwZELoG4Vo9FLA9NciiBI5S6Y4mm6Elfjm1S03JQ=; Received: from p54ae91f2.dip0.t-ipconnect.de ([84.174.145.242] helo=localhost.localdomain) by ds12 with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.89) (envelope-from ) id 1l0NoV-0006Y0-Ds; Fri, 15 Jan 2021 13:02:47 +0100 From: Felix Fietkau To: linux-wireless@vger.kernel.org Cc: johannes@sipsolutions.net Subject: [PATCH v3 9/9] mac80211: minstrel_ht: fix rounding error in throughput calculation Date: Fri, 15 Jan 2021 13:02:42 +0100 Message-Id: <20210115120242.89616-10-nbd@nbd.name> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20210115120242.89616-1-nbd@nbd.name> References: <20210115120242.89616-1-nbd@nbd.name> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On lower data rates, the throughput calculation has a significant rounding error, causing rates like 48M and 54M OFDM to share the same throughput value with >= 90% success probablity. This is because the result of the division (prob_avg * 1000) / nsecs is really small (8 in this example). Improve accuracy by moving over some zeroes, making better use of the full range of u32 before the division. Signed-off-by: Felix Fietkau --- net/mac80211/rc80211_minstrel_ht.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/net/mac80211/rc80211_minstrel_ht.c b/net/mac80211/rc80211_minstrel_ht.c index 6496aa39f60b..9e010c8dd063 100644 --- a/net/mac80211/rc80211_minstrel_ht.c +++ b/net/mac80211/rc80211_minstrel_ht.c @@ -445,10 +445,9 @@ minstrel_ht_get_tp_avg(struct minstrel_ht_sta *mi, int group, int rate, * (prob is scaled - see MINSTREL_FRAC above) */ if (prob_avg > MINSTREL_FRAC(90, 100)) - return MINSTREL_TRUNC(100000 * ((MINSTREL_FRAC(90, 100) * 1000) - / nsecs)); - else - return MINSTREL_TRUNC(100000 * ((prob_avg * 1000) / nsecs)); + prob_avg = MINSTREL_FRAC(90, 100); + + return MINSTREL_TRUNC(100 * ((prob_avg * 1000000) / nsecs)); } /* -- 2.28.0