From patchwork Thu Nov 2 14:07:05 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Konstantin Khlebnikov X-Patchwork-Id: 833374 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=yandex-team.ru header.i=@yandex-team.ru header.b="YLU0eskT"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3ySRjl54Zvz9sNw for ; Fri, 3 Nov 2017 01:07:23 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933256AbdKBOHM (ORCPT ); Thu, 2 Nov 2017 10:07:12 -0400 Received: from forwardcorp1o.cmail.yandex.net ([37.9.109.47]:33907 "EHLO forwardcorp1o.cmail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933057AbdKBOHL (ORCPT ); Thu, 2 Nov 2017 10:07:11 -0400 Received: from smtpcorp1o.mail.yandex.net (smtpcorp1o.mail.yandex.net [IPv6:2a02:6b8:0:1a2d::30]) by forwardcorp1o.cmail.yandex.net (Yandex) with ESMTP id 9A3A3206FD; Thu, 2 Nov 2017 17:07:08 +0300 (MSK) Received: from smtpcorp1o.mail.yandex.net (localhost.localdomain [127.0.0.1]) by smtpcorp1o.mail.yandex.net (Yandex) with ESMTP id 97FEB2440DC6; Thu, 2 Nov 2017 17:07:08 +0300 (MSK) Received: from unknown (unknown [2a02:6b8:0:460:c5ab:eccf:e6e6:3148]) by smtpcorp1o.mail.yandex.net (nwsmtp/Yandex) with ESMTPSA id qkC2yioFYX-78xqWSLK; Thu, 02 Nov 2017 17:07:08 +0300 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client certificate not present) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex-team.ru; s=default; t=1509631628; bh=Y6GXVpdJTXXMD85gyEeg2XRjA9+vHO00lXep5MTrLcs=; h=Subject:From:To:Cc:Date:Message-ID; b=YLU0eskT+8SDZN2fAMkwLYPpcDE2E5u6n2f7RNrQ76cinRbtZev2E7iVzC7+5N5jS 6z/S80tdNZb3EHgolJ6x79g9Vj3mDcvBh9rqnvoU0P9pNS5DAyrN+qNt7cR0Tc72fU uNhTIFsRkM14Qrff/+//X0Inm01uu9SrAY0wjwtY= Authentication-Results: smtpcorp1o.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Subject: [PATCH] tcp_nv: use do_div() instead of expensive div64_u64() From: Konstantin Khlebnikov To: netdev@vger.kernel.org, "David S. Miller" Cc: Stephen Hemminger , Lawrence Brakmo , linux-kernel@vger.kernel.org, Eric Dumazet Date: Thu, 02 Nov 2017 17:07:05 +0300 Message-ID: <150963162556.169720.4979222608705024316.stgit@buzz> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Average RTT is 32-bit thus full 64-bit division is redundant. Signed-off-by: Konstantin Khlebnikov Suggested-by: Stephen Hemminger Suggested-by: Eric Dumazet --- net/ipv4/tcp_nv.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c index 125fc1450b01..17e290ffcd80 100644 --- a/net/ipv4/tcp_nv.c +++ b/net/ipv4/tcp_nv.c @@ -209,7 +209,7 @@ static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample) struct tcp_sock *tp = tcp_sk(sk); struct tcpnv *ca = inet_csk_ca(sk); unsigned long now = jiffies; - s64 rate64 = 0; + u64 rate64; u32 rate, max_win, cwnd_by_slope; u32 avg_rtt; u32 bytes_acked = 0; @@ -251,8 +251,9 @@ static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample) } /* rate in 100's bits per second */ - rate64 = ((u64)sample->in_flight) * 8000000; - rate = (u32)div64_u64(rate64, (u64)(avg_rtt ?: 1) * 100); + rate64 = ((u64)sample->in_flight) * 80000; + do_div(rate64, avg_rtt ?: 1); + rate = (u32)rate64; /* Remember the maximum rate seen during this RTT * Note: It may be more than one RTT. This function should be